The Food Lab's Complete Guide to Buying, Storing, and Cooking Prime Rib

The Food Lab

Unraveling the mysteries of home cooking through science.

Everything You've Ever Wanted To Know About Prime Rib.




Essential techniques, recipes, and more!

I've cooked a lot of beef in my life. Most recently, it was 58 pounds of the tasty animal matter that came delivered by Pat LaFrieda to Serious Eats world headquarters in the form of two whole prime-grade, grass-fed, dry-aged, grain-finished, well-marbled, hormone-free, Black Angus prime ribs. Beautiful hunks of meat that have left my apartment semi-permanently perfumed with the sweet, musky scent of crisp beef fat, not an altogether unpleasant state of affairs.

But wait—prime-grade? Grain finished? Marbled? "What do all these terms mean?" you cry. And more importantly, "Why should I care?"

Here are the answers to every question you've ever had or might ever have about prime rib.


So what exactly is Prime Rib?

To locate the prime rib, start by cutting your favorite cow neatly down the center from head to tail along the spine. Set aside one half for another use. Place your hand on its back and feel your way backwards along its vertebrae until you start feeling ribs. Count backwards to the sixth rib (this is called, appropriately enough "Rib #6"), and cut here.

Now continue counting back until you get to Rib #12 and cut again. Reserve the head section and the tail section for another use, saving just the ribs you just cut out. Now saw the ribs off at about 13 to 16-inches down their length and set aside the belly section. Take off the hide, and what you're left with is the prime rib.

It consists of seven full ribs with a large eye of meat running along their back side. This meat is part of the loin muscle of the cow, the exact same muscle that New York strips, rib-eyes, and Delmonicos are cut from. It's also often referred to as a "standing rib roast," because, well, you roast it, it's from the ribs, and it stands up.

Wait a minute—do humans have prime ribs too?

Absolutely, though ours would most likely not be as tender as a cow's. You see, a cow spends much of its time standing on four legs eating grass (or grain, as the case may be). Its back muscles do very little work, and consequently are very tender. Humans stand upright and do things like bend, lift, jog, and poke fires with sticks. Our backs get more of a workout, producing muscle fibers that are tougher, but probably more flavorful.


So why would I want to eat a little-exercised portion of a cow, and what does marbling mean?

Two things: tenderness and fattiness. The loin muscle of a cow is one of the most tender cuts available, perhaps beaten out only by the tenderloin (aka filet mignon, where a chateaubriand comes from). Its advantage over the tenderloin is that it contains a generous amount of fat, both in large swaths around the central eye of meat, and more importantly, within the muscle itself in a web-like network known as marbling.

Why is this marbling important? Mainly because it lubricates the muscle fibers. At room or fridge temperature, it's a solid fat, but once cooked, it melts, helping muscle fibers slip around each other more easily as you chew, resulting in more tender, juicier meat. Marbling is also important because most of the flavor in red meats come from the fat. Indeed, there are studies in which tasters fed portions of lean beef and lean lamb are unable to identify them correctly, despite being easily able to do so when given a portion with fat. Fatty beef tastes beefier.


Here's something that's always confused me: does "Prime Rib" have anything to do with "Prime Grade" beef?

I'm really glad you asked. The answer is no.

The term "Prime Rib" has existed longer than the USDA's beef grading system, which classifies beef according to its potential tenderness and juiciness into various grades. It's called Prime Rib because it's the best part of a given cow. After the USDA began introducing its labeling system denoting quality of beef and included the label "prime" as the highest quality, things became a little confusing.

These days, it's possible to buy a "Prime Rib" that is also "Prime Grade," but it doesn't necessarily have to be so. My local Whole Foods sells "Choice Grade Prime Ribs," for example.

A full, seven-rib prime rib is a massive hunk of meat, between 20 to 30 pounds. That's too big to fit into my oven in one piece, which is why I, like most people, buy my prime rib in three or four rib sections. These sections have different names depending on where they are cut from:

  • Ribs 6 through 9, which comes from closer to the cow's shoulder (aka the chuck) are referred variously as the "chuck end," "blade end," or "second cut." It's got more separate musculature, and more large hunks of fat. Personally, I prefer this end, because I like to eat the fat in a well-roasted piece of beef. If you prefer leaner, more tender beef, then go for...
  • Ribs 10 through 12, taken from further back and known as the "loin end," "small end," or "first cut." It's got a larger central eye of meat, and less fat.

Depending on what part of the country you live in, your butcher will refer to those cuts as various different things, but all of them should know which ribs are which, so ask for "ribs 6 through 9" or "10 through 12," and you should be fine.

Can you tell me a bit more about the USDA grading system?


Happy to oblige. Cattle are graded after slaughter according to the degree of marbling, as well as the cow's age.

Starting from the top, there's "Prime", which denotes an abundant degree of marbling in a cow under 42 months of age. Only about 2% of the beef sold in this country is designated Prime, and most of it goes to restaurants and specialty butchers.

Next is "Choice", the standard option at high-end supermarkets like Whole Foods, for example. Below that is "Select" which is what you'll find in most standard supermarkets and accounts for the majority of beef destined for the table. These cows have a slight amount of marbling, and must be under 30 months of age.

Below select come terms like "Commercial", "Utility", "Cutter," which seem more apt to describing scissors than organic matter.

In the photo above, you can clearly see the larger degree of marbling on the lefthand roast, which is Prime grade, versus the right, which is Choice.

But Prime-graded beef is so expensive/difficult to find. Is it really worth seeking out and paying for?

Good question. I held a blind beef tasting pitting Choice grade beef against Prime, cooking both in the exact same manner and to the same temperature (oh the horrors I put up with in the name of science!). Of the eight tasters present, there was an overwhelming and unanimous preference for the Prime-graded beef, though the Choice was still quite tasty.

Prime generally costs about 25% more per pound then Choice, which is a hefty chunk of change for your standard 8 to 10 pound roast feeding 10 people. Then again, I save my prime rib for the holidays—a special occasion that deserves a special piece of beef.


Going back to the photo above... I can see that marbling, but why is the one on the left also much darker than the one on the right?

Ah, you've got a good eye. Here's the reason: it has to do with the conversion of one of the muscle pigments, myoglobin, and its exposure to oxygen. Immediately after being cut, the color of meat is a dark, purplish color—the color of myoglobin— Soon, oxygen will begin to interact with the iron in myoglobin, converting it to oxymyoglobin, which has a bright, cherry red color. Have you ever noticed how when you cut into a rare steak in an oxygen-rich environment (like your house) it starts out dark then "blooms" into redness? Now try the same thing in the vacuum of outer space. See the difference?

The prime rib on the left was freshly trimmed moments before shooting the photograph, while the one on the right was bought from the butcher counter, where it had been sitting exposed to oxygen for several hours, at least. Even though the bright cherry red color is the one most associated with freshness, it's really got nothing to do with it.

Eventually, enzymes present in the meat will cause both myoglobin and oxymyoglobin to lose an electron, forming a pigment called metmyoglobin. It's got a dirty brown/gray/green color. While it doesn't necessarily indicate spoilage, it does mean that the beef has been sitting around for a while.

Do you mean to tell me that the color of beef doesn't come from blood?

Precisely that. Beef you buy in the supermarket contains little to no blood. Blood contains a very similar pigment called hemoglobin. But if somebody if somebody orders their beef "bloody," and really mean it, they will be sorely disappointed.


What's all this business about dry aging?


Ah, now we get into the seriously expensive beef. Dry aging is the process by which whole cuts of beef are kept in precisely temperature and humidity controlled environments for periods of up to several months in order to promote certain changes in its structure:

  • Tenderization occurs when enzymes naturally present in the meat act to break down some of the tougher muscle fibers.
  • Flavor change is probably the most relevant. Due to numerous reasons including oxidation and enzymatic and bacterial action, properly dry-aged meat will develop deep nutty, cheesy aromas.

The longer meat is aged, the more pronounced these effects. Three-month dry-aged meat, with its intense blue-cheese-like flavor can taste downright rancid to some people. Most prefer aging of around 30 to 40 days, like the prime rib pictured above.

Because it requires skill, equipment, and more importantly, lots of space and time to properly dry-age meat, you can expect another 20 to 25% premium for dry-aged beef.

Is dry-aging worth it, and is there any way I can do it myself at home?

In our blind tasting of dry-aged beef, tasters placed it unanimously and unequivocally above all other samples. It's the single best way to absolutely guarantee a tender and flavorful steak, so yes—it's worth it if you can find it.

Unfortunately, dry-aging requires that you use entire, untrimmed-portions of beef. During the process, the outer layers of beef get completely desiccated and must be trimmed off. Because of this, and because of the equipment required, dry-aging at home is not impossible, but not for beginners! Check out our complete guide to dry-aging beef at home for more details if you're really curious!

Natural, Grass-Fed, and Organic

Labels sometimes confuse me. What do "natural," "grass-fed," and "organic" really mean?

Labeling laws in the United States are confusing at the very least, and in many cases, worthless. Bear in mind that it's also not in the best interest of the vast majority of beef producers to make the labeling any clearer—the less the consumer knows about how meat gets on their table, the better.

Most cattle in this country are grown in high-density feed lots. They are fed a GMO corn and soy-based diet, treated with antibiotics to stave off the diseases they'd get from being in such cramped, dirty quarters, and to promote faster growth, and are generally treated significantly worse than your average scum-of-the earth. Why we continue to allow this to happen is another question entirely, but you'll be happy to know that as a consumer, you can help prevent it, and get better quality, healthier, tastier meat in the process.

Here are a few labels you might see in the market, and what they mean:

  • Natural means basically nothing. There's no enforcement; there are no rules. It's basically an honor system between the producer and the customer, but no third party checks it.
  • Naturally raised, on the other hand, does mean something. As of 2009, the label ensures that the animals are free of growth promotants and antibiotics, except coccidiostats for parasites, and that they were never fed animal byproducts.
  • Organic beef is certified and inspected by the government and must be fed completely organic feed grains and must be antibiotic and hormone free. They must also have access to pasture, though in reality this "access" could be a single patch of grass on the far side of a large dirt feedlot. Organic cattle are also subject to stricter enforcement of humane treatment. Very recent legislation mandates that at least 30% of their dry matter intake needs to come from pasture for 120 days out of the year. That's good news.
  • Grass-fed cattle must, at some point in their lives, have been raised on a diet of grass. They do not necessarily receive a 100% grass diet, nor are they necessarily finished on grass. Most "grass-fed" cattle are fed grain for their last few weeks to fatten them. The very definition of what "grass" means is also up to debate. Many producers want to include young corn stalks under the umbrella of "grass," effectively diluting the label.


Is it true that there is a restaurant called Milliways that serves cows that have been bred to actually want to be eaten?

Don't believe everything you read. And don't forget your towel.

Grass-fed Beef: Health and Flavor

Is "grass-fed" beef really healthier than grain-fed?

Many studies indicate that it is. It's certainly healthier for cows, a ruminant animal whose digestive system has evolved to break down grass. According to NYU professor Marion Nestle, grass-fed cows tend to have lower levels of E. coli, require fewer antibiotics, and have lower levels of dangerous bacteria in their feces, making them all-in-all safer to consume. They also tend to have higher levels of omega-3 fatty acids (that's the healthy stuff), as well as a higher level of trans conjugated linoleic acids (CLA's).

Wait—isn't that a trans-fat, and aren't trans-fats those horrible things that Mayor Bloomberg banned from New York?

Yes indeedy. The very same trans-fats that occur in artificially hydrogenated fats are present in the meat of all ruminants, like cattle, sheep and goat. So if you live in New York, you can't get your trans-fats in chips anymore, just stroll into the butcher section of any supermarket for your fix. How's that for hypocrisy?

However, there is an indication that CLA's from cows are actually healthier than the artificial trans-fats from hydrogenated oils. It's unclear whether it's real nutritionists who think this, or perhaps just someone from the Beef Council. As with most matter related to nutrition, the literature seems to indicate that nobody really knows what the heck is going on.

I'm getting sick of all this talk about health and nutrition. What about flavor?

Grass-fed beef in general has a more robust, slightly gamier flavor than grain-fed beef, and if it's grain-finished, it'll be just as tender and moist. Personally, I try and find beef from a produce who I know has allowed the cattle to graze for the majority of their life on pasture, then finished them with grain. Creekstone Farms, who supplies a lot of Pat LaFrieda's beef is one such producer, and is available in some specialty butchers in New York. Your best bet is to get to know your butcher, and talk to him about what you want. How you balance flavor, nutrition, and ethics is up to you.

Portion Control and Cooking Time

And just how much beef should I buy anyway?

In general, you should plan on about one pound of bone-in prime rib per guest, which translates to about one rib section for every two people. Each pound of raw, bone-in prime rib will give you about a half pound of edible cooked meat.

I've got my beef, so now can I just follow a timing chart to know when it's cooked?

No, no, no! Do yourself a favor and throw out every roasting timing chart you have. The only reliable way to tell when your beef is done is to use an accurate thermometer, like the Thermapen from ThermoWorks. No matter what cooking method or oven temperature you use, as long as the center of your meat never goes above the right temperature, you'll be guaranteed the right results.


  • 120°F (rare): Bright red and slippery on the interior. Abundant intramuscular fat has yet to soften and render.
  • 130°F (medium-rare): The meat has begun to turn pink, and is significantly firmer. Juicier, moister, and more tender, and beefier than either rare or medium meat.
  • 140°F (medium): Solid rosy pink, and quite firm to the touch. Still moist, but verging on dry. Fat is fully rendered at this stage, delivering plenty of beefy flavor.
  • 150°F (medium-well): Pink, but verging on gray. Moisture level drops precipitously, Chewy, fibrous texture. Fat has fully rendered, and has begun to collect outside the steak, carrying away flavor with it.
  • 160°F (well done): Dry, gray, and lifeless. Moisture loss is up to 18%, and fat is completely rendered. What once was cow, now is dust.

Here's what you should shoot for (these temperatures are a good 10 to 20°F lower than USDA guides, which tend to overshoot everything).


Here's one for you: bone-in, or bone-out?


I've always wondered about this one myself, so I ran a series of tests. The idea that many chefs propose is that cooking meat on the bone is always a better idea, as the bone adds lots of flavor. I'm skeptical.

First of all, most of the flavor found in a bone is deep inside, in the marrow. If you've ever tried to make a stock out of just bones, you'd find that it's almost tasteless unless the bones are cracked. Secondly, I've shown numerous times that as far as flavor penetration goes, there's very little movement of molecules across a piece of meat. Even marinating overnight will only get you a couple millimeters of penetration. What chance does any flavor from the bone have of getting into the meat?

To test this, I cooked four identical roasts. The first was cooked with the bone on. For the second, I removed the bone, but tied it back against the meat while cooking. For the third, I removed the bone, and tied it back to the meat with an intervening piece of impermeable heavy-duty aluminum foil. The fourth was cooked completely without the bone.

Tasted side-by-side, the first three were completely indistinguishable from each other. The fourth, on the other hand, was a little tougher in the region where the bone used to be.

What does this indicate? Well, first off, it means the flavor exchange theory is completely bunk—the completely intact piece of meat tasted exactly the same as the one with the intervening aluminum foil. But it also means that the bone does serve at least one important function: it insulates the meat, slowing its cooking, and providing less surface area to lose moisture.

Bottom line: the best way to cook your beef is to detach the bone and tie it back on. You get the same cooking quality of a completely intact roast, with the added advantage that one its cooked, carving is as simple as cutting the string, removing the bones, and slicing.


Does it really matter when I salt my meat?


Absolutely. Take a look at the picture above, which shows the same piece of salted meat with photos taken about 13 minutes apart. In the top row, the salt is still in large crystals, just beginning to dissolve. Because of a phenomenon known as osmosis, the salt will initially draw liquid out of the meat and onto the surface. By the 25 minute mark (bottom left corner), those juices form distinct droplets on the meat's surface. Meat cooked at this stage will lose moisture fast, giving you a leathery crust.

Eventually, as we hit the 40-minute mark, the salty meat juices have begun to react with the muscle fibers themselves, dissolving some of their proteins, and causing the structure of the meat to open up, like a sponge. The extracted meat juices soon get reabsorbed, and the salt goes along for the ride. The result is better, more deeply-seasoned beef.

Given a few days, unlike a marinade, salt can actually slowly work its way deeper into the meat. I like to heavily salt my prime rib at least four days before roasting before covering it with plastic wrap and placing it in the fridge.

And don't forget to put salt on the table as well—after you slice that beef, there's a huge expanse of pink meat in the center that needs to be seasoned too!

Cooking Method

I've heard that searing meat at a high temperature right at the start of cooking will "lock in juices," resulting in a moister finished product. Is this true?

Nothing could be further from the truth. In my thorough exploration of this very question last year, I found that meat seared before roasting loses a good 1.68% more juices than meat seared after roasting.


A much more effective way to cook your beef is to start it in very low temperature oven (around 200°F) until it comes to the desired finished temperature, then remove it and blast it in a 500°F to brown it just before serving. If you've got a convection setting on your oven, use it.

Isn't this also the best way to ensure that your meat is perfectly cooked from edge to edge?


Indeed it is. Cook a large hunk of meat at a high oven temperature, you'll cook it fast, but you'll also create a large doneness gradient. The center may be perfectly medium rare, but the outer edges will be overcooked. Low, slow heat is the best way to ensure that your meat is rosy pink from edge to edge.


Other Techniques

What about fancy-pants chefs who cook their ribs sous-vide or sear them with various pieces of industrial machinery?

Leave the fancy-pants methods to the fancy-pants. In my experience, cooking large roasts—whether prime rib or turkey—in a sous-vide water oven certainly guarantees perfectly, evenly cooked results, but a lot of the deep, roasted flavor notes you get from meat roasted in the open air are completely absent. It's also a pain in the butt to try and vacuum-seal an entire prime rib. I much prefer mine done in a low temperature oven.


As for torching, it looks really cool, but the results are not worth the trouble. Torching before roasting gives you a surfaces that's nearly burnt in spots and barely browned in others, while torching after roasting doesn't do nearly as good a job as a hot oven or roasting pan set over a couple burners does.

Serving a Picky Crowd

I've got another question, and it's a doozy: my dainty aunt likes her meat rare, but my tempestuous brother prefers his well-done. What's an understanding and generous host to do?

First off, you should wonder how your brother was created out of the same genetic material as you. After that, you should take his portion from the perfectly medium-rare beef, slice it, and either toss it in the microwave for a few minutes, or back into the oven until it is the desired shade of dry.

The Recipe

You want a foolproof prime rib recipe that'll guarantee perfect results?
Check it out here »



Wow, that worked great! Thanks! But Gramps decided not to show up for dinner—what's the best way to store his leftovers?

An all too common dilemma. For short term storage, your best bet is to just tightly wrap it in plastic, and keep it in the fridge. It'll last for around three days, after which you should start checking for spoilage. Bear in mind that rare or medium-rare meat may turn brownish (remember myoglobin?) in the fridge. This isn't necessarily a sign of spoilage. Just follow your nose!

For longer term storage of larger pieces of either cooked or uncooked meat, you'll want to freeze it. If you've got a vacuum sealer, use it. Air is the enemy of frozen food, causing it to dry out in an irrevocably process known as freezer burn. If you don't have a vacuum sealer, wrap the meat tightly in foil (plastic wrap is not airtight), then a few layers or plastic wrap, and place it in the freezer. The plastic wrap helps keep the foil tightly against the surface of the meat, while the foil prevents air from coming in contact with it.

Let your meat defrost in the refrigerator. This can take a couple days for larger cuts of meat.

Did I hear that right? Plastic wrap is not air-proof?

That's correct. Air can still travel through plastic wrap, though quite slowly.

And what about reheating?

If you are wise, you will have been slicing meat to order, leaving you with a large chunk of leftovers rather than many thin slices. The best way to reheat a large chunk of meat is to treat it like you would a steak, which after all, it is: warm it in a low oven to the desired internal temperature, then sear is in a hot skillet to crisp up and brown the exterior. Alternatively, the microwave is surprisingly effective. Just don't let the meat go above the temperature you initially cooked it to.

If you've already sliced your steak, your best option is sandwiches and salads. Still delicious!

And as for those bones, either feed them to Dumpling or Chichi.