I can guarantee you will not be disappointed when you try this Grilled Tomato Herb Flank Steak. It’s so simple and the delicious tomato, vinegar and herb marinade doubles as the mop sauce, which transforms the grass-fed steak into a tender and juicy dinner to remember!

steak and cucumbers on a black plate

I originally developed this recipe for EatingWell Magazine and it appeared in the July August 2009 issue. I then shared this recipe here on July 15, 2011. I have updated the blog images and some of the text today.

Last summer, my friends went out to dinner at a much hyped restaurant that features mostly local ingredients. It had gotten great reviews and the chef had crafted a menu with a seemingly innovative use of local ingredients including cheeses, produce and grass-fed beef from local farms. My one friend (being the meat-enthusiast that he is) was happy to see the grilled steak on the menu. Afterwards, I asked him how the meal was. His review? Let’s just say the meal did not convert him from the Costco-buying, grain-fed-burger-grilling-camp to out and out smug locavore. I think he said something like his steak “tasted like an old dairy cow.” I almost peed I laughed so hard because that is exactly what grass-fed beef tastes like if you don’t know the tricks to making it taste good. I hoped he would give it another try.

a close up of tomato marinated steak

I know I say this every time I do a grass-fed beef post, but it deserves to be repeated: Grass-fed beef is a lot lower in fat than “conventional” beef. [Cringe, I don’t like using that expression “conventional.” What is even close to conventional about feeding a ruminant corn? Sheesh!] As a result it can tend to dry out if it is cooked too long. So you have to watch it, and when in doubt, turn it. Another thing about the fat: Grass-fed fat is healthier fat too.

a platter of flank steak and a plate with cucumbers and steak

Tips for Cooking Grass-Fed Beef

Season It

  • The biggest challenge is balance of flavor. If you do nothing but just season the heck out of it, you are already off to a much better start than just slapping the meat on the grill.
  • Grass-fed beef loves strong flavors like any allium relative (I’m talking about garlic, onion or shallot.) It also is really nice when it is paired with woody herbs such as thyme, rosemary and my fave marjoram.
  • And for the love of all things good, don’t forget the salt. If anyone sees an apron that says “needs salt” buy it for me, I’ll pay you back.

Marinate It

  • Something with a good deal of acid like vinegar or citrus really works its way into the meat. I’m not sure if I buy into the whole thing about marinating making meat more tender. As far as I can tell marinating only really tenderizes the outer layer of the cut of meat. If at all.
  • But marinating does help with the whole dairy cow thing my friend was talking about. In other words, grass-fed beef can be a little gamey, akin to lamb or even venison. But if you marinate it in a boldly-flavored marinade you balance those flavors.
  • And if you are blessed with enough time, marinating a cut like flank steak for a full 24 hours is worth the wait.

Don’t Over-Cook It

As I said, grass fed beef is lean, so ere on the side of cooking it a little less than you normally would. And I recommend turning it more often, too. After the first couple of times you’ll get the hang of it and be a grass-fed beef cooking pro!

sliced flank steak

What I love about this Grilled Tomato Herb Flank Steak is that some of the marinade is set aside before you add the meat to be used as a mop sauce. Basting the mop over the meat as it’s grilling gives you even juicier flavor. I’m not sure that this recipe will keep my friend out of the Costco meat department all together, but it may be enough to open him up to giving grass-fed beef another try.

Today I paired this delicious Grilled Tomato Herb Flank Steak with my simple skinny cucumber salad. It would also be great with Ratatouille which is in season right now. And leftovers would be great for Steak Salad. But since steak and potatoes are kind of a thing, check out a few of my yummy potato side dishes.

What To Serve With This Steak Recipe 

potatoes with herbs and butter

simple buttermilk mashed potatoes

healthy roasted garlic mashed potatoes

vegan potato salad with herbs

potatoes with butter and herbs

grilled potatoes

herbed smashed new potatoes

Grilled Flank Steak with Tomato Herb Mop Sauce is a simple paleo-friendly dinner featuring grass-fed flank steak. | Healthy Seasonal Recipes | Katie Webster #paleo #grilling #grassfedbeef

grilled tomato herb flank steak

  • Author: Katie Webster
  • Prep Time: 45 minutes
  • Cook Time: 12 minutes
  • Total Time: 24 hours
  • Yield: 6 servings 1x
  • Category: Main Course
  • Method: Grilling
  • Cuisine: American


You will not be disappointed when you try this Grilled Tomato Herb Flank Steak. It’s so simple and the delicious marinade doubles as the mop sauce, which transforms the grass-fed steak into a tender and juicy paleo-friendly dinner to remember!



  • 1 medium slicing tomato, such as beefsteak, cored and chopped
  • 1 shallot peeled and quartered
  • ¼ cup red wine vinegar
  • 2 tablespoons chopped marjoram
  • 1 tablespoon chopped rosemary
  • 1 teaspoon salt
  • ½ teaspoon freshly ground pepper
  • 1 ½ pounds flank steak, preferably grass-fed, fat trimmed


  1. Puree tomato, shallot, vinegar, marjoram, rosemary, salt and pepper in blender until smooth. Reserve ½ cup for mop. Scrape the remaining tomato mixture into a re-sealable plastic bag. Add steak and turn to coat. Refrigerate 4 hours or overnight.
  2. Prepare grill to medium high heat. Remove steak from marinade and discard any left-over marinade. Oil grill rack. (see how to do that in this post.) Grill steak about 5 minutes per side for medium-rare, 6 to 7 minutes per side for medium and 8 minutes per side for medium-well; after turning meat brush first cooked side with mop.   Brush mop over second cooked side and remove to a platter to rest 5 minutes. Slice against the grain and serve with any remaining mop spooned over sliced meat.


0 g Added Sugar, 85 mg Cholesterol


  • Serving Size: 3 1/2 ounces each
  • Calories: 164
  • Sugar: 0 g
  • Sodium: 289 mg
  • Fat: 6 g
  • Carbohydrates: 1 g
  • Fiber: 0 g
  • Protein: 25 g

sliced flank steak

collage of flank steak with tomatoes