Marinade for Flat Iron Steak on Grill

Use ingredients you probably already have in the kitchen to make this Flat Iron Steak Marinade. It turns an affordable piece of beef into something juicy, tender and super flavorful.

You will love this Flat Iron Steak Marinade!

Unpopular opinion, but filet mignon is overrated. Yes, it’s very tender, but I don’t think it actually has that much flavor.

I much prefer a cheaper cut of meat, even if it needs a marinade. Cuts like flank steak and skirt steak can be SO tender and flavorful if prepared properly (and perfect wrapped in a tortilla with fajita toppings!).

And recently, I’ve discovered something called a flat iron steak.

Just like crock pot ribs, even with a homemade dry rub recipe, are a much cheaper but still delicious alternative to a big double cut pork chop, flat iron steaks are a more affordable way to get your beef fix. And dare I say, a grilled flat iron steak is way tastier than filet mignon, especially when paired with watermelon feta salad and potato salad with bacon.

Today, I’m sharing my favorite marinade for a flat iron steak. It’s very likely you can make this with ingredients you already have in your kitchen! As you’ll see below, just like homemade salad dressings like creamy feta dressing, it’s VERY adaptable for what you have on hand.

What is a flat iron steak?

A flat iron steak is a cut from the shoulder of a cow (just like my country style pork ribs recipe come from the pig’s shoulder). It is sometimes called a “top blade roast” or “patio steak.”

The entire top blade of the cow generally weighs between two and three pounds, and most butchers cut that into 4 flat iron steaks (about 8 to 12 ounces each).

Flat iron steaks generally have quite a bit of fat marbling running throughout them, which is what help makes them so tender and flavorful.

My favorite thing about flat iron steaks is how they are almost perfect rectangles, and are an even thickness throughout. That takes some of the guesswork out of grilling them!

Flat iron steak is perfect tucked into steak lettuce wraps or perched on top of steak tostadas or butternut squash noodles.

Flat Iron vs Flank Steak

A flat iron steak comes from the shoulder area of a cow, while the flank steak comes from the abdominal area. Flat iron is known for its marbling and tenderness, while flank steak is leaner.

What is Flat Iron Steak good for?

Flat iron steak is a versatile cut that can be grilled, broiled, pan-seared or even sous-vide. It can be used in a variety of dishes, like fajitas, stir-fries, steak sandwiches, or simply enjoyed on its own.

Ingredients for Grilling Flat Iron Steak

• flat iron steak – you’ll need a 1 pound flat iron steak for this recipe. If you don’t see it out, ask your butcher!
• vegetable oil – or you can use olive oil here, but vegetable oil is much cheaper and I think it’s just fine for a marinade!
• soy sauce – there’s no salt in this marinade for a flat iron steak, as all of the salt comes from the soy sauce. Don’t skip it! Soy sauce is also the secret ingredient in my homemade gravy.
• onion – you just need a small hunk of onion, roughly chopped. I usually use white or yellow onion, just depending on what’s in my fridge. I’ve even used a couple of green onions when I have them.
• garlic – you will need 1 clove of garlic for this flat iron steak marinade recipe. Use the rest of your garlic to make honey roasted carrots to go with your steak, or garlic dip recipe for snacking!
• orange juice – you can actually use ANY citrus juice here. I had oranges, but if you have lemons already on hand for citrus salad dressing, use those! Limes work too! If you use oranges, zest them first and make a orange bundt cake for dessert.
• brown sugar – this adds sweetness to the marinade. If you have dark brown sugar, you can use that instead (it can also be used in my microwave caramel sauce).
• chili powder – this adds a little mild heat to the marinade.
• cumin – this adds a warm, earthy flavor to the steak (and my kafta recipe).
• giardiniera – optional, but one of my favorite garnishes for this cut of steak. I buy a jar of prepared mild (but you could do hot if you prefer) giardiniera, which is a pickled Italian relish made with peppers, celery, carrots and cauliflower. I roughly chop it and spoon it over the steak for serving.
• flaky sea salt – I prefer Maldon brand, and I can’t eat a steak without a sprinkle of it!

How to cook a Flat Iron Steak on the Grill

You can cook a flat iron steak in a cast iron skillet on the stove (like my orange glazed chicken), or even under your oven’s broiler, but my favorite way to cook it is to grill it.

After marinating, remove your steak from the marinade and let any excess marinade drip off. Bring the steak to room temperature for about a half hour before grilling. Optional, but if you want to sprinkle your steak with a little of my best rib rub, I won’t fight you on that.

Preheat your grill for direct grilling over medium-high heat. Transfer the steak to the grill and sear each side for 2 minutes.

Then, reduce the heat to medium and continue to grill the steak, turning occasionally, until the center of the meat reaches 130 degrees F for medium-rare*. This should take about 10 to 12 minutes of total grilling time.

Transfer the grilled flat iron steak to a plate and lightly cover with foil. Let stand 5 minutes before thinly slicing across the grain and serving.

*I grilled my steak to a very rare doneness (120 degrees F when I pulled it off the grill), as that’s how my family likes to eat it. If you like it more done, grill until 140 degrees for medium doneness. I don’t ever recommend going over this for good steak.

How long to marinate flat iron steak:

Just like with root beer ribs, it’s best to marinate flat iron steak for at least four hours so that the flavors can start to soak into the meat, and the acidity can tenderize the steak.

You can also marinate overnight! However, try not to marinate longer than 24 hours if you can help it.

After TOO long, the acid in this flat iron steak marinade recipe will start to “cook” the beef (like how lime juice “cooks” the shrimp in shrimp ceviche), and the steak will be a little tough once you grill it.

A little secret about this flat iron steak marinade recipe:

My little secret is that I don’t measure anything when making this marinade (or my buttermilk chicken marinade or balsamic steak marinade, for that matter). Well, except the one time I measured so that I could include measurements in the recipe card below.

But every other time, I literally just eyeball every ingredient. Life is too short to have to clean a bunch of measuring cups and spoons for a marinade for a flat iron steak. Save those utensils for a baked good like Baileys brownies.

The exact ingredient amounts aren’t important here. As long as the general proportions are correct, the end result will be delicious.

So, go ahead, use a chunk of onion, a few squeezes of orange, a spoonful of brown sugar, and some dashes of spices. Honestly, you don’t need to measure anything for this flat iron steak marinade recipe.

How to garnish Grilled Flat Iron Steak

A perfectly grilled flat iron steak doesn’t really NEED much aside from a sprinkle of flaky sea salt.

But, I also love a little something acidic served with it to cut through the fatty richness of the meat.

I often serve it with a drizzle or balsamic glaze or a spoonful of chimichurri sauce made with both red wine vinegar and lemon juice.

Sometimes I’ll spoon blistered tomatoes over sliced steak.

When I don’t have tomatoes or herbs on hand, my favorite shortcut garnish for grilled steak is jarred giardiniera.

Giardiniera is an Italian relish of pickled vegetables. It is usually made with peppers, celery, carrots and cauliflower.

You can buy a spicy version (or even add your own pickled jalapenos – see my post about how to pickle jalapenos), but I like the mild. I buy the Delallo brand. It is intensely bright and fresh and vinegary. I’m sure there are lots of other brands that are good, too.

I just give the giardiniera a rough chop and spoon it over the sliced steak. It doesn’t get any easier!

What to serve with this flat iron steak recipe:

I’ll never turn down mashed potatoes with this grilled flat iron steak recipe, and mashed potatoes with heavy whipping cream and blue cheese mashed potatoes are both great options.

For a fresh veggie side dish, try balsamic asparagus, balsamic green beans or maple glazed Brussels sprouts.

If it’s a hot summer day, cool down with a cold pasta salad like seafood pasta salad or goat cheese pasta salad.

What other steaks can you use this marinade for?

I also love this flat iron steak marinade recipe for flank steak, skirt steak and hanger steak. All of these cuts are relatively inexpensive, can be tenderized very well with a simple marinade, and are full of flavor.

How to store Grilled Flat Iron Steak

If you have leftovers of grilled flat iron steak, allow them to cool to room temperature. Then, place them in an airtight container and refrigerate up to 3 days. You can also freeze up to 3 months.

Grilling Flat Iron Steak FAQs