Marinated and Grilled Flat Iron Steak

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This flat iron steak marinade is SO simple to throw together and lends delicious flavor and juiciness to tender grilled flat iron steak. Red wine, balsamic vinegar, and a handful of pantry staples shine in this balanced marinade and the grilling steps could not be quicker.

A dinner plate of steak, potatoes, and green beans.

I would be hard-pressed to pick my favorite steak cut, but flat iron steaks are always a crowd favorite. Ultra tender, very receptive to a marinade, and flexible to be cooked a variety of ways, it's an all-purpose kitchen MVP that isn't too pricey, to boot.

This easy flat iron steak marinade (with simple grilling instructions) has turned into my go-to preparation for this lean cut of steak.

Note: You may find packaged steak already sliced into smaller cuts (like seen in these photos) or in a larger steak. I prefer making multiple smaller steaks as you can grill them each for their own amount of time if they're of different thicknesses. Plus I like the extra surface area for soaking up the marinade.

Reasons to Love This Recipe

It's really simple! Just about all of the ingredients are pantry or fridge staples.
Red wine and balsamic vinegar provide a bold, super flavorful base to the steak marinade that shines through to the grilled flat iron steak.
While this marinade would be a great option for many steak varieties, it pairs with the tenderness and marinade-friendliness of the flat iron cut perfectly.

Recipe Ingredients

Labeled flat iron steak marinade ingredients on a marble board.

Steak: One-and-a-half pounds of steak is used here. The kind I buy splits the 24 ounces into four steaks. Ideally the pieces will be around the same thickness/size so they cook evenly, but if not, simply alter the grill time for each so they're as you like them.
Wine: Use a red wine on the drier side, such as Pinot Noir, Cabernet Sauvignon, or Merlot. And you don't need anything fancy, just a variety that you wouldn't mind drinking (or cooking with) the rest of as this marinade uses only one-half cup.
Oil: Olive oil provides a lot of moisture and helps temper the bolder wine and vinegar flavors.
Balsamic vinegar: The sharpness of balsamic vinegar pairs really well with the lush wine flavor for a balanced and bold marinade.
Worcestershire sauce: Just one tablespoon works to amplify the "beefiness" of steak and ties all of these marinade flavors together.

Step-by-Step Instructions

Add all of the marinade ingredients (except for the steak) to a large plastic bag. A gallon-size bag works well. I place it in a mixing bowl and fold out the top edge, as seen in the photo below, so it can stand up and not tip over. Whisk the marinade right in the bag until all of the ingredients are evenly combined.

A whisk in a large plastic bag filled with the flat iron steak marinade.

Add the steaks to the bag, press out any excess air, then seal. Flip the bag over and turn the steaks around to fully coat all sides of them with the marinade. Place the bag in the refrigerator and marinate for at minimum 2 hours, but ideally 6-8 for the best flavor.

Flat iron steak marinating in a sealed plastic bag.

Let the grill heat to medium-high temperature for 10 minutes to ensure it's nice and hot, as this grilled flat iron steak doesn't take long to cook. Cook for 4 minutes per side for medium-rare doneness (or to however you like). Let the steak rest briefly before serving.

A whole flat iron steak on a plate with potatoes and green beans.

Recipe Tips and Tricks

Place the bag of marinating steak on its side to more effectively cover the surface of the steaks. Also place the bag on a plate or in a large enough baking dish in the fridge to contain a spill in case the bag leaks.

Faced with extra steak? I make this leftover steak sandwich every time. The flavor of this marinade matches up so nicely with the horseradish aioli and sauteed onions.

It's best to oil the grill grates to prevent sticking, and it's easiest to do this before turning the grill on. Rub clean grill grates with a paper towel that's been dipped in a neutrally-flavored cooking oil that's friendly to higher heat cooking, such as canola oil, corn oil, vegetable oil, etc.

A digital instant-read thermometer is one of my most-used kitchen tools. As all grills can cook a little differently, taking the internal temperature of steaks is the most foolproof way of cooking them to exactly the doneness you like.

A sliced steak with mashed potatoes and green beans.

Recipe FAQs

Is flat iron steak tough?

Not at all. Cut from the top blade/shoulder region, sinews and tough connective tissues have been removed to form this particular cut. It has a nice amount of fat marbling within to yield a very tender steak.

Is flat iron steak good for grilling?

Yes. Because it's tender it doesn't require a longer cook time to break down connective tissues, and its even, not-too-tall thickness across the different cuts means they won't take a long time to grill (just about four minutes per side).

What's good to serve with grilled flat iron steak?

Delicious side dish pairings for steak include garlicky sauteed green beans, mashed potatoes, roasted broccolini, any kind of side salad, and spicy sauteed asparagus, which can also be grilled to streamline dinner prep.

Either jammy red wine or bold balsamic vinegar adds to the delicious flavor of these reader-favorite main dish recipes.

If you’ve enjoyed this recipe, I’d love for you to leave a star rating in the recipe card and/or a comment review below!