Flat Iron Steak Marinade

This flat iron steak marinade is savory, balanced, and made with simple pantry ingredients such as soy sauce, garlic, and Dijon mustard. It delivers juicy, tender steak for grilling or easy weeknight dinners—and fair warning: once you make it, you’ll wonder why you ever marinated steak any other way.

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For more steak recipes, check out my Steak Soup and Creamy Chimichurri Steak Pasta.

Grilling season is one of my favorite times of year, and a great marinade is always the key to a truly memorable steak. This flat-iron steak marinade is one I come back to again and again because it’s simple to make, deeply flavorful, and consistently delivers juicy, tender results.

Made with pantry staples like soy sauce, olive oil, garlic, Dijon mustard, and a touch of brown sugar, this marinade strikes the perfect balance of savory, tangy, and slightly sweet. It’s designed specifically to enhance flat iron steak—a flavorful, budget-friendly cut that shines when marinated and cooked over medium-high heat.

Whether you’re planning a casual weeknight dinner or firing up the grill for a summer cookout, this marinade makes cooking flat-iron steak feel effortless and special.

If you’re loving grilling recipes lately, don’t miss my Asian Tri-Tip Steak, Grilled Balsamic Chicken Thighs, Pork Chop Marinade, and Mexican-Inspired Chicken Marinade.

Important Ingredients and Substitutions

Flat Iron Steak — A tender, flavorful cut from the shoulder that’s great for grilling and marinating. If you can’t find it, flank steak, skirt steak, hanger steak, or sirloin work well with this marinade—just adjust cooking time based on thickness.

Reduced-Sodium Soy Sauce — Provides the savory backbone of the marinade without making it overly salty. Tamari or coconut aminos can be used for a gluten-free option, though coconut aminos will add a touch more sweetness.

Red Wine Vinegar — Adds acidity to help tenderize the steak and balance the richness. Balsamic vinegar or Worcestershire sauce can be substituted in a pinch, but the flavor profile will shift slightly.

Dijon Mustard — Adds depth and helps emulsify the marinade so it coats the steak evenly. Smooth Dijon works best, but whole-grain Dijon can be used if that’s what you have.

Brown Sugar — Balances the saltiness and acidity while helping the steak caramelize on the grill. Honey or maple syrup can be substituted for a slightly different sweetness.

Dried Rosemary — Adds an earthy, aromatic note that pairs well with beef. You can substitute about 1½ teaspoons of fresh minced rosemary if preferred.

Recipe Variations

Not only is this marinade delicious and beginner-friendly, it’s also easy to adapt to your taste preferences and what you have on hand. Here are a few simple twists to try:

• Honey Garlic Marinade — Swap the brown sugar for honey and add an extra clove of garlic for a slightly sweeter, sticky finish that caramelizes beautifully on the grill.
• Worcestershire Boost — Add 1 tablespoon of Worcestershire sauce for extra depth and umami. This works especially well if you’re serving the steak with potatoes or grilled vegetables.
• Herb-Forward Steak Marinade — Add fresh chopped rosemary or thyme (about 1½ teaspoons) in place of dried herbs for a brighter, more aromatic flavor.
• Spicy Steak Marinade — Add ½–1 teaspoon red pepper flakes or a splash of hot sauce to the marinade for gentle heat that doesn’t overpower the steak.
• Asian-Inspired Twist — Add 1 teaspoon of sesame oil and finish the grilled steak with sliced green onions and sesame seeds. This variation is great for serving the steak over rice or in stir-fries.

How to Marinate Flat-Iron Steak

For the complete recipe and measurements, scroll to the recipe card at the bottom of this post.

Step 1: Add the soy sauce, red wine vinegar, olive oil, salt, minced garlic, rosemary, Italian seasoning, Dijon mustard, brown sugar, and black pepper to a mixing bowl.

Step 2: Whisk until well-combined.

Step 3: Place the flat iron steak in a shallow dish or a resealable plastic bag. Pour the marinade over the steak, turning to coat it evenly. Cover and refrigerate for 6–12 hours.

Step 4: About 20–30 minutes before cooking, remove the steak from the refrigerator. Letting it come closer to room temperature helps it cook more evenly.

How to Cook Flat-Iron Steak (Grilling and Stovetop)

This marinade works beautifully whether you’re grilling outdoors or cooking steak indoors. Both methods deliver juicy, flavorful results—just choose what works best for you.

On the Grill

Preheat the grill to medium-high heat (375°F–400°F) and lightly oil the grates if needed. Remove the steak from the marinade and discard the marinade.

Grill for 7–11 minutes, turning every 2–3 minutes, until the steak reaches your desired level of doneness. Let rest for 5–10 minutes before slicing.

On the Stovetop (Pan-Seared)

Heat a large, heavy skillet (such as a cast-iron skillet) or a grill pan over medium-high heat with a small amount of oil.

Pat the marinated steak dry with a paper towel, then sear for 4–6 minutes per side, depending on thickness and doneness. Rest the steak for 5–10 minutes before slicing.

Chelsea's Recipe Pro-Tips

• Marinate for the full time if you can. Flat iron steak benefits from a longer soak, and 6–12 hours gives the marinade time to fully penetrate the meat for maximum flavor and tenderness.
• Turn the steak while marinating. If possible, turn the steak once or twice during the marinating time so it absorbs the marinade evenly on all sides.
• Let the steak temper before cooking. Taking the steak out of the fridge 20–30 minutes before grilling helps it cook more evenly and prevents a cold center.
• Substitute other cuts if needed. This marinade also works well with flank steak, skirt steak, hanger steak, or sirloin—just adjust cooking time based on thickness.
• Cook over medium-high heat. This cut does best with hot, direct heat, which creates a flavorful crust while keeping the inside juicy.
• Always rest before slicing. Letting the steak rest for 5–10 minutes allows the juices to redistribute, giving you a more tender, flavorful bite.

Storage Directions

• Storing: Leftover cooked steak can be stored in an airtight container in the refrigerator for 4–5 days.
• Freezing: For best results, freeze the raw steak in the marinade in a freezer-safe container or resealable bag for up to 3 months. Thaw overnight in the refrigerator before cooking.
• Reheating: Reheat leftover steak gently in a skillet over low heat or briefly in the microwave on low heat to avoid overcooking. Flat iron steak is best enjoyed freshly cooked, as reheating too aggressively can dry it out.

Serving Suggestions

This flat iron steak pairs easily with both cozy comfort sides and lighter vegetables. Try it with cream cheese mashed potatoes or scalloped sweet potatoes for something rich and satisfying, then add air fryer broccolini or air fryer portobellos for balance.

For a classic touch, creamed peas make a simple, nostalgic side, and a basket of no yeast dinner rolls is perfect for rounding out the meal—especially on busy weeknights when you still want something warm and homemade.

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4.82 from 16 votes

Flat Iron Steak Marinade

Chelsea Plummer | Mae's Menu

This flat iron steak marinade is savory, balanced, and packed with flavor from soy sauce, garlic, and Dijon mustard. It creates juicy, tender steak every time and works beautifully for grilling or pan-searing.

Prep Time 10 minutes mins

Cook Time 15 minutes mins

Marinating Time 8 hours hrs

Total Time 8 hours hrs 25 minutes mins

Course Main Dish

Cuisine American

Servings 6 Servings

Calories 243 kcal

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Ingredients

  

1x2x3x

• ⅓ cup reduced-sodium soy sauce
• 2 tablespoons red wine vinegar
• 1 tablespoon olive oil
• ½ teaspoon salt
• 1 tablespoon minced garlic
• ½ teaspoon dried rosemary
• ½ teaspoon Italian seasoning
• ½ teaspoon smooth Dijon mustard
• 1 ½ tablespoons packed light brown sugar
• freshly cracked black pepper to taste
• 1 ½ to 1 ¾ pounds flat iron steak

Instructions

 

• In a medium mixing bowl, whisk together the soy sauce, red wine vinegar, olive oil, salt, minced garlic, rosemary, Italian seasoning, Dijon mustard, brown sugar, and black pepper until fully combined and the brown sugar has dissolved.
• Place the steak in a shallow dish or resealable plastic bag. Pour the marinade over the steak and turn to coat evenly. Cover and refrigerate for 6 to 12 hours, turning the steak once or twice if possible.
• Remove the steak from the refrigerator 20–30 minutes before cooking to allow it to come closer to room temperature.
• Preheat the grill to medium-high heat (375°F to 400°F). Clean and lightly oil the grill grates if needed.
• Remove the steak from the marinade and discard the marinade. Place the steak on the grill and cook for 7–11 minutes, turning every 2–3 minutes, or until the steak reaches your desired degree of doneness.

Notes

• Marinating time matters. For the most flavorful and tender steak, marinate for at least 6 hours and up to 12 hours. Even a shorter marinate will add flavor, but longer time delivers the best results.
• Let the steak rest. After grilling or pan-searing, let the steak rest for 5–10 minutes before slicing to keep it juicy.
• Substitutions. To make this recipe gluten-free, use tamari or coconut aminos instead of soy sauce. Honey or maple syrup can be used in place of brown sugar for a slightly different sweetness.
• Other cuts of steak. This marinade also works well with flank steak, skirt steak, hanger steak, and sirloin—just adjust cooking time based on thickness.
• Storage & freezing. Leftover cooked steak can be stored in the refrigerator for 4–5 days. For best results, freeze the raw steak in the marinade for up to 3 months, then thaw it in the refrigerator before cooking, as cooked steak does not freeze well.

Nutrition

Serving: 1gCalories: 243kcalCarbohydrates: 4gProtein: 23gFat: 14gSaturated Fat: 5gPolyunsaturated Fat: 1gMonounsaturated Fat: 6gTrans Fat: 0.4gCholesterol: 75mgSodium: 794mgPotassium: 414mgFiber: 0.2gSugar: 3gVitamin A: 4IUVitamin C: 0.5mgCalcium: 19mgIron: 3mg

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