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It’s almost Labor Day, it’s still hot, and we’re still grilling! 

My partner, Richard, also known as DW, has been right by my side raising our kids for 11 years, since we first “blended” our families. He is known for this steak recipe. We clamor for it regularly, and DW is always ready to drop what he’s doing to get it marinated and onto the grill. He makes it for just us, for a crowd, at home, and on the road when we’re trying out another Airbnb or descending on kind friends.

This is a briny, slightly sweet, tender sliced steak. Our go-to is flank steak, but this marinade is for any cut of beef that needs a little coaxing to be its most tender and flavorful, so it’s also great for hanger steak and skirt steak. And the marinade can easily be doubled or quadrupled if you’re feeding a crowd and don’t want to spend a million dollars doing it.

It goes like this:


1 flank steak (2–2½ lbs)

1 medium red onion, diced, about 1 cup

4 cloves garlic, finely minced

2 T capers, roughly chopped

½ cup balsamic vinegar

1 t salt 

½ t black pepper

¼ cup olive oil

a few sprigs of parsley for garnish (optional)


  • With a small paring knife, pierce the steak all over on both sides at roughly 2-inch intervals, without piercing through to the other side. (You don’t want deep cuts, just small, shallow incisions for the marinade to work into.)
  • Combine all the ingredients except the steak in the marinating container of your choice—a pyrex dish, a Ziploc bag, or a large plastic Tupperware. Add the steak and turn a few times to coat evenly. Marinate in the refrigerator for at least 2 hours but preferably for 8 hours or overnight. (DW throws it together early in the morning to grill later the same evening.) Be sure to turn the steak over several times in the marinade, even if your marinating time is short.
  • An hour before grilling, take the steak out of the refrigerator and remove from marinade to a platter to come to room temperature. Pour the marinade into a small saucepan and reserve.
  • Get your grill ready. If using gas just turn it on to highest heat. Cook for 5 minutes on each side for medium rare at the thickest part of the steak. If using charcoal light your coals. The coals should be white hot. Bank the coals to one side at the bottom of your grill. Place steak on grill over the coals and sear for 2 minutes on each side then move to the side of the grill away from the coals and cook for another 3 minutes per side for medium rare. If you prefer the steak to be medium it will only need another minute on each side whether using gas or charcoal.
  • Remove steak to platter to rest for 10 minutes. While the steak is resting add 2 T of grainy mustard to the reserved marinade, bring to a simmer and reduce slightly. Taste for seasoning. You may want to add a little more olive oil if it tastes too acidic.
  • Slice the steak thinly, against the grain. Drizzle with the reduced marinade and serve.

A tomato salad, potato salad, and corn are all great accompaniments.

Thanks, DW!

File it!

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About The Author

For Sarah Ross, everyday cooking is about winging it—with a classic or an old favorite recipe given to her by a friend. These are the recipes that get stained with spills from being on repeat, the ones to share.


  • Sarah, I actually have All the other ingredients in my pantry right now, so this may be on our dinner table this week. Well, not that particular mustard nor the flank steak itself…but close enough! Love the presentation. You make it look great for company.

  • Write a cookbook! Absolutely delicious.

  • Thank you for the recipe. Flank steak is our very favorite.

  • Yummy

  • This marinade sounds delicious. However, from a food safety perspective it is not recommended to serve used marinade with the meal. Instead, prepare extra marinade for this purpose.

    • The marinade is simmered and reduced, so it would be fine to eat after that (just like the marinade on the steak itself gets cooked and is therefore safe.)
      Plus—given how many times it sounds like they have made this meal, I would say they know what they are talking about!

    • Sarah says the reserved marinade is brought to a simmer before serving which should make it perfectly safe to eat.

    • Yes, that red flag went up for me too! Just make extra.

      • Notice that the reserved marinade is cooked prior to serving.

  • Yum! This is a must-try recipe. Thank you for sharing.

  • This looks great! We’ll do this over the weekend!

    • Ate it. Loved it!

  • I have a standard marinade that doesn’t include capers or mustard. This looks like just the ticket for the weekend!

  • Sarah, was delighted to find two of my fav Go-To’s (red onion and balsamic vinegar) in this recipe; marinades that do the “heavy lifting” are my dinner “jam!!” Thank you for sharing your family recipe for success!!

  • Oh Sarah this looks so good!!

  • Just made this for dinner! It was delicious and delightful! Thank you!

  • Wow! I don’t even have a grill and I want to try this. I think the next time I go to a barbecue get-together I can take this ready to be put on

  • Wow, thanks for all the comments. DW and I are honored that you’ve added his recipe to your rotations!

  • Made this last night since we’re having a weird November heatwave, and husband said let’s grill. Delicious!!! The only things I changed were combining balsamic and merlot vinegar (we were low on balsamic), and I added sherry to the simmered marinade sauce.

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