Grilled Flank Steak

Prep: 8 min Cook: 10 min Total: 18 min Servings: 3
Annie Lampella @ Ketofocus

By Annie Lampella, Pharm.D.

Published July 21, 2023 • Updated February 1, 2026

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BBQCarnivoreEasySummer Grilling

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For a tender, juicy steak that you can BBQ in less than 10 minutes, make this grilled flank steak recipe. Marinated in a tangy, aromatic mustard herb mixture, this keto grilling recipe is the ideal dish for a flavorful yet effortless low carb meal.

This grilled marinated flank steak is tender, juicy and ultra-savory. Grilling brings out the natural robust, beefy flavor while adding a smoky char similarly to a ribeye or high-end steaks. But this inexpensive cut of beef cooks quickly requiring less than 10 minutes due to the steak’s thinness and the hot sear cooking method. Those juices are locked in from the caramelized crust, keeping the inside of beef flank steak succulent.

Medium rare slices of steak spilling juices on a white platter and covered with chopped parsley.

We used an oil-based marinade for this steak recipe. The neutral oil provides a vessel for the flavors of the herbs, garlic and mustard to season the meat evenly. Adding red wine vinegar to the steak marinade helps to tenderize the meat. The tanginess from the vinegar and mustard combined with the fresh cilantro and parsley have a resemblance to chimichurri sauce.

How to grill flank steak?

The best way by far to cook flank steak is on the grill, and it’s one of my favorite keto dinners during the summer. This butcher’s cut steak typically has a large surface area so it’s able to pick up a nice char and smoky flavors. Flank steak has a close-grained texture that makes it ideal for grilling anywhere between a rare and medium cook. Cooking the flank beyond medium and you can get chewy, rubbery steak. Like other butcher’s steaks, flank steak should be grilled over high heat, flipping it occasionally, until it develops a nice crust on both sides.
  1. Preparation: Take the steak out of the refrigerator and allow it to come to room temperature for about 30 minutes. This helps the steak to cook evenly.
  2. Marinade: Flank steak doesn’t soak up marinades quite as well as similar quick cooking cuts like hanger or skirt steak, but it still gives a nice boost of flavor. Try the delicious mustard-herb marinade made by combining stone ground mustard, fresh cilantro and parsley with red wine vinegar and garlic. Marinate for 2-8 hours. 
  3. Grilling flank steak: Very high heat is essential to grilling flank steak – 450 – 500˚F. Since it is relatively thin, you want to give the beef a nice char before it overcooks. Grill the steaks from start to finish over this high heat, flipping occasionally. Usually takes about 3-5 minutes per side, depending on the thickness of the steak and desired level of doneness.
  4. Resting: Like any meat, flank steaks should be allowed to rest for a few minutes after cooking.
  5. Slicing: Use a long, thin sharp carving knife to slice the steak against the grain.
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Grilled Flank Steak

Prep 8m Cook 10m Total 18m 3 servings

Ingredients

  • 18 oz flank steak
  • 3 tablespoons avocado oil or neutral oil
  • 2 tablespoons minced parsley
  • 2 tablespoons minced cilantro
  • 2 tablespoons stone ground mustard
  • 1 tablespoon red wine vinegar
  • 3 cloves garlic, minced
  • 1 1/2 teaspoons salt

Step by Step Instructions

Step by Step Instructions

1
Prepare steak

Pat steak dry with a paper towel on all sides. Place steak in a large baking dish, plate or Ziploc bag.

Patting steak dry with a paper towel.
Tip Most butchers sell flank steak trimmed and ready to cook.
Ingredients for this step
  • 18 oz flank steak
2
Make flank steak marinade

In a small bowl, whisk together avocado oil, minced parsley, minced cilantro, mustard, vinegar, garlic and salt.

A small glass dish with herb marinade inside.
Tip 1 teaspoon of garlic powder can be substituted for fresh garlic; however, fresh herbs are preferred
Ingredients for this step
  • 3 tablespoons avocado oil
  • 2 tablespoons minced parsley
  • 2 tablespoons minced cilantro
  • 2 tablespoons stone ground mustard
  • 1 tablespoon red wine vinegar
  • 3 cloves minced garlic
  • 1 1/2 teaspoons salt
3
Marinate flank steak

Rub or brush steak marinade all over the meat. Let marinade soak in for at least 1-2 hours but up to 8 hours. Refrigerate while marinating.

A large chunk of beef marinating in a herb garlic marinade in a baking dish.
Tip Don't let flank steak marinate longer than 10 hours or else the meat can get chalky and firm from the vinegar.
4
Grilling flank steak

Thirty minutes before cooking, remove the flank steak from the refrigerator and allow beef to come to room temperature for even cooking. Preheat one side of the grill to high (450 – 500˚F). Once the grill is hot enough, place the flank steak on the hot side of the grill and cook until well charred, about 3-5 minutes. Flip and continue to cook until the second side is well charred, about 3 minutes more. Transfer the steak to the cooler side of the grill, cover and cook until the internal temperature is 125˚F for medium-rare or 135˚F for medium.

A piece of steak grilling on a gas grill.
Tip If using a charcoal grill, light up an entire chimney of coals and pile them all under one side of the grill. As soon as the coals on top are hot, add the steak and cook as instructed.
5
Let rest

Transfer steak to a cutting board and allow to rest for at least 5 minutes before slicing the steak against the grain to serve.

Slicing steak against the grain with a knife and fork.
Nutrition Per Serving 6 oz steak
410 Calories
28g Fat
36g Protein
1g Net Carbs
1g Total Carbs
3 Servings
Nutrition disclaimer

The nutrition information provided is an estimate and is for informational purposes only. I am a Doctor of Pharmacy (Pharm.D.); however, this content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always consult your physician or other qualified health provider before making any lifestyle changes or beginning a new nutrition program.

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Grilled Flank Steak

Frequently Asked Questions

How long to grill flank steak?

Flank steak grills relatively quickly because it's a thin cut of beef plus it should be grilled over a very hot barbeque (about 450-500 ˚F). It should take about 3-5 minutes per side to cook flank steak on the grill to a medium doneness. This will vary depending on the thickness of the steak and heat from the grill.

Can I use a grilling pan or cast iron skillet to cook the flank steak over the grill?

Yes, you can transfer the marinated steak to a cast iron skillet to cook over the barbeque grill; however, flank steak generally has a large surface area, so you might need to cut the steak up into smaller pieces before grilling in a skillet.

Can yellow mustard be used in place for stone ground mustard?

In a pinch, yes, you can use yellow mustard in place of stone ground mustard. Dijon mustard can be used in this steak marinade too.

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Juicy, tender slices of steak on a plate with parsley sprinkled on top.

What is flank steak

Flank steak is a cut of beef taken from the belly, towards the rear end of the steer. It’s a great alternative to premium steaks because it’s usually less expensive compared to ribeyes yet is still tender and juicy if cooked correctly. Flank is a wide, flat, rectangular cut of beef with a moderately beefy flavor, has plenty of juice and a strong grain. Since it’s on the thinner side, this steak lends itself perfectly to the grill especially if feeding a crowd. It’s naturally low carb with zero carbs per serving. It cooks in a matter of minutes over very high heat, but is still thick enough where you can achieve a nice medium-rare center.

Another name for flank steak

Flank steak is also called London Broil or Jiffy Steak. It may also be sold as stir-fry beef at the grocery store, but this will usually come pre-sliced.

Selecting the perfect flank steak

When shopping for the best flank steak, look for an even deep red color with a fair amount of fat running along the muscle. Avoid cuts that still have a thin membrane attached or the surface of the meat is shredded. You want a nice smooth surface without nicks or gouges from a butcher’s knife.

Skirt steak vs flank steak

Flank steak is not the same as skirt steak; although, both are flavorful cuts of meat that are just as tender and juicy as expensive cuts of steak when cooked correctly (usually on a grill over very high heat). But here is how they differ:
  • Location – Both come from the belly of cow; however, the outside skirt is the diaphragm muscle of the steer.
  • Texture & grain – Flank steak is leaner, more compact and has a more pronounced grain. Skirt has loose texture and can easily become tough and leathery if overcooked.
  • Size & shape – Skirt steak comes in a long, thin strip while flank steak is wider, more rectangular shaped and is a bit thicker.
  • Flavor – Skirt steak has a beefier more robust, buttery flavor compared to flank.
 

Flank steak substitute

If you can’t find this cut of beef at your grocery store, luckily there are substitutes for flank steak. These are ideal to replace flank because they can be cooked the same way, have a similar flavor and are considered thin cuts of steak. Substitutes for flank steak include skirt steak, hanger steak and flap meat. All work great for keto grilling.
A platter with sliced flank steak cooked medium rare on it. Half of the steak is sliced and other other is whole. A fork and parsley are nearby.

How to cut flank steak

When it comes to trimming, flank steak is usually pre-trimmed by the butcher with membranes removed and ready to cook. After it’s cooked, flank steak should be cut against the grain similar to other cuts of beef. The grain of meat refers to the direction that the muscle fibers are going. These are long, parallel lines that run along the steak. To cut against the grain, position your knife 90 degrees from the direction of the grain. Cut into thin pieces about 1/4 to 1/2 inch thick.  

Simple flank steak marinades

If cooked correctly, flank steak can be tender with a mild, beefy flavor, so you don’t need to add much of a marinade. Generally, simple marinades are the best and will let your steak take center stage. Besides the herb-mustard marinade above, here are some other simple marinades to try:
  • Herb garlic – Mix 1/4 cup olive oil, 4 cloves smashed garlic, 1 tablespoon whole black peppercorns, 1 teaspoon fennel seeds, 1/2 cup chopped parsley, 1/2 teaspoon fresh thyme, 2 tablespoons soy sauce, 1 1/2 teaspoons salt. Marinate for at least 6 hours.
  • Steak sauce – Make your own A-1 steak sauce by adding 1/2 cup Worcestershire sauce, 1/4 cup soy sauce, 3 tablespoons brown sugar free sweetener, 2 cloves smashed garlic, 2 tablespoons Dijon mustard, 2 tablespoons tomato paste, 1/2 cup avocado or neutral oil. Marinate for at least an hour.
  • Cilantro lime –  Uses fresh cilantro and lime juice. It’s best served over rice or sliced up for flank steak tacos
  • Fajita – A unique fajita marinade that uses soy sauce and has a similar flavor to the flank steak fajitas you would find at a Mexican restaurant.
 

Recipes that use flank steak

Although I prefer to enjoy my flank steak as a steak or even with a side of chimichurri sauce, there are other ways you can use flank steak.
About the Author
Annie Lampella, Pharm.D.

Annie Lampella, Pharm.D.

Annie is a Doctor of Pharmacy, mom, and the recipe creator behind KetoFocus. With a B.S. in Genetics from UC Davis, she has over 14 years of experience developing family-friendly keto recipes based on the science of human metabolism.

Learn more about Annie View My Cookbook

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