A tuna steak may be the color of red meat, but to my mouth, swordfish is the fish that offers the most steak-like eating experience. Buttery, juicy, and meaty, swordfish has a substantialness that few other creatures of the ocean can match.
Grilling it is one of the best ways to bring those meaty qualities to the fore. It's easy to do, relying on only a few important steps: choosing the right piece of swordfish, preparing the grill correctly, and grilling the steaks just right.
How to Choose Swordfish Steaks for Grilling
Swordfish rarely arrives at your local fish market whole—it's just too big of a fish. This makes it harder to determine the freshness of what you're buying. You can't check the clearness of the eyes or the pinkness of the gills, or use any of the handful of other methods we recommend for judging freshness when you're planning to cook a whole fish. With swordfish, you have only a few ways to determine if it's still good to eat.
It's difficult to judge the freshness of swordfish by looks alone, but it doesn't hurt to consider appearances. Look for swordfish steaks that are light in color, ranging from cream to gently pink to ivory. What you don't want is swordfish flesh that's turned a dull brown tint. Swordfish also has some darker muscle tissue that runs through it, which can turn a deeper brown with age; if there's a slight reddish tint, that can suggest freshness.
A better measure is smell. Like all fish, swordfish at the market should never be stinky or smell unpleasantly fishy. Instead, it should have a faint and distinctly clean fish aroma. These can be difficult for some folks to tell apart—isn't any fishy smell a bad smell?—but there is indeed a difference. Think of it this way: You want your fish to smell like a pleasant ocean breeze, not like the docks after a day in the hot sun.
There's an additional consideration when you're choosing swordfish for grilling: size. Fish, being a more delicate protein than, say, beef, has a tendency to stick and fall apart on the grill. Swordfish is more robust than many flakier options, but it can still meet that fate.
This is easy enough to avoid if you follow our grilling instructions below, but before any of that, you want to choose swordfish steaks that won't make things harder than necessary.
The thickness of the steak is most important. You want a piece of swordfish that's about one to one and a half inches thick. Any thinner, and it'll be more likely to bend and break when you try to flip it; it'll also be more likely to cook through before the fish has fully released from the grill (more on that below). You'll end up with a difficult choice: attempt to remove the fish when it's properly cooked but risk breaking or tearing it, or leave it on longer to ensure it's easy to remove but risk overcooking it.
The overall size of the steak is the other consideration. There's nothing wrong with trying to grill a large cross section of swordfish, but the bigger the slab of fish, the more likely it is to break when you flip and lift it. It's just like trying to flip a massive pancake—the bigger it is relative to the spatula size, the higher your chances of ruining it during the flip.
It's best to buy a very large piece of swordfish and then cut it into smaller portions yourself, or you can ask your fishmonger to portion the fish for you.
How to Grill Swordfish Steaks: Step by Step
Step 1: Prep Your Grill
Setting up your grill for swordfish steaks follows the same basic best practices for grilling anything else. You want to preheat your grill and grill grate, clean the grate well with a grill brush, and oil the grate. A hot, clean, and oiled grill grate will be much less likely to severely stick to your fish than a gunky, cold one.
I recommend setting your grill up for a two-zone fire, which means spreading the lit charcoal over one half of the charcoal grate while leaving the other half empty. This allows you to sear the fish over high heat, and then move it, if necessary, to a cooler portion of the grill to finish cooking over indirect heat.
Whether or not you need to do the finishing step over indirect heat will largely depend on the thickness of your fish. A thinner swordfish steak may be done as soon as both sides are nicely seared, while a thicker one may need a few extra minutes for the heat to penetrate more deeply to the center.
Step 2: Prep the Swordfish Steaks
While your grill is preheating, you can prep your fish. This might include portioning it into more manageable sizes, if that still needs to be done. You'll also want to dry the fish well on both sides, using paper towels, which will help speed up the searing process and reduce the chances that the swordfish sticks to the grill.
To that end, another thing I like to do is lightly rub the dried steaks with a neutral oil, like canola or vegetable oil. It's just one more bit of insurance against sticking.
Step 3: Grill the Swordfish
When your grill is ready and your fish is ready, it's time to grill. Season the fish all over with salt and, if you want, pepper. Remember: Pepper is a spice and therefore always optional, while salt is a fundamental flavor agent—absolutely required, unless you're on a salt-restricted diet.
Salt draws moisture out of proteins like fish and other meats, so I make sure to sprinkle it on the swordfish at the last second. After we've made sure to dry the surface of the fish well, the last thing we want to do is get it wet again right before putting it on the grill.
I start by setting the swordfish steaks over the hotter section of the grill to get a good initial sear on the first side. Even with all of the preparations we've made, the fish will still likely stick to the grill grate at first, so do your best to refrain from attempting to lift or move the steaks prematurely. They should release on their own once they've browned well.
If the fish has adhered to the grill grate at all, the best way to release it isn't to try to jam a metal spatula underneath. Instead, slide a thin metal tool, like the tines of a carving fork, or even the spatula blade itself, down between the grill grates and under the fish. Then gently lift from below, being careful not to force it if it's stuck on tight.
Now turn the fish and repeat on the second side. As you can see in the photos here, I've put a crosshatch pattern on the swordfish steak by rotating it roughly 45 degrees partway through searing on each side. Is that necessary? No, absolutely not. There is no benefit to trying to brand the fish with a diamond pattern, aside from the fact that it kinda looks nice. It comes with a risk, too, which is that in order to do it, you need to lift and rotate the fish even earlier than if you just left it until it was time to flip. So, do it or don't do it; it's up to you.
If the fish isn't cooked through to your desired doneness at this point, allow it to finish cooking over the cooler area of the grill, flipping and rotating it every minute or two for even cooking.
Step 4: Determining Doneness
This gets us to the last question: How do you know when your grilled swordfish steaks are done?
The two main factors that will determine doneness are the thickness of your swordfish steaks and the heat of the grill, which, in turn, is determined by a dizzying number of variables, including the type and quantity of charcoal you're using, its distribution on the charcoal grate, how long it's been burning, the distance between the grill grate and the charcoal, and where exactly on the grill you've placed your fish.
It is, in short, impossible to give any meaningful time estimates for doneness, and you should be wary of any recipes that do.
In my experience, if you're cooking over direct heat, you can usually get a good sear on each side of a swordfish steak in about four or five minutes, give or take a couple minutes here or there. That's all you need for the exterior—a good sear. But you still need to make sure it's cooked nicely in the center.
For me, perfectly cooked swordfish is somewhere in the zone of medium to medium-well, where there's still a portion of slightly translucent flesh in the center that's warmed through, but not chalky or dry. Others might want their fish more well-done. The USDA says you should cook fish to 145°F (63°C) in the center to make sure you've killed any possible pathogens. That's well-done in the world of fish, and too hot for my tastes, but if you want to follow their guidelines, there you go.
I prefer to aim for an internal temperature closer to about 130°F (54°C) for swordfish. Keep in mind, though, that when you're attempting to take the temperature of a piece of fish this thin, moving the probe even one millimeter in one direction or another can give you a different reading. As accurate as a good thermometer has the potential to be, it's not perfect in this scenario. Kenji has described how to account for this in his article on how to use an instant-read thermometer.
In short, you push the probe all the way through the piece of meat, then slowly draw it back up until you find the inflection point where the temperature is lowest. That should help you hit close to the true temperature center. Even so, it's not a guarantee.
That's why I also employ a totally unscientific method that I've developed over years of cooking, and one that I think everyone else should try to cultivate as well: psychic doneness readings. That's right. On this empirically driven cooking website, I'm encouraging you to imagine the heat penetrating into the fish, and use a sense of intuition to help guide you.
Okay, I'm kidding about the psychic part, but in all seriousness, intuition is an essential part of cooking ability. It takes some experience to become good at it, and it's certainly not foolproof, but when you combine it with a thermometer, you'll tend to get better results than either method alone is likely to deliver.
On more occasions than I can count, I've overridden the numbers my instant-read thermometer was telling me based on nothing more than a carefully honed gut feeling, and saved the meal as a result. Not because my thermometer was broken or inaccurate, but because I knew that it had limitations of its own, especially on thinner cuts like this. Like self-driving cars and automatic pilot systems on airplanes, cooking still requires some degree of human oversight to make corrections when the machines fail us. And they do fail us.
You are the last safeguard against poorly cooked food. Don't ruin pricey swordfish steaks by forgetting that.