Grilled Mustard-Marinated Flank Steak with Charred Scallion Salsa

By , Test Kitchen Director · Reviewed by AislePrompt Editorial · ·

Juicy flank steak marinated in tangy mustard and garlic, grilled to perfection and topped with a vibrant charred scallion salsa. This american-inspired beef ready in about 30 minutes blends flank steak, Dijon mustard, olive oil into a versatile sauce that lifts everything from grain bowls and roasted vegetables to grilled proteins — a small-batch staple worth keeping in the fridge. Each serving lands at about 320 calories and feeds 4, so a small batch covers several meals across the week without taking over the fridge. Tap "Plan a meal with the AI" below to drop this recipe into your week and send the ingredients straight to Instacart. Nutrition values are approximate, calculated from USDA FoodData Central (fdc.nal.usda.gov) — verify against ingredient labels for any health-driven dietary plan.

Prep: 15 min Cook: 15 min Serves 4 American cuisine 320 cal/serving
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Ingredients

Instructions

  1. Step 1: In a medium bowl, whisk together 3 tbsp Dijon mustard, 2 tbsp olive oil, 4 minced garlic cloves, 2 tbsp soy sauce, 1 tbsp brown sugar, 1 tsp salt, and 1/2 tsp black pepper to form a marinade. Place 1.5 lbs flank steak in a large resealable bag and pour marinade over it. Seal and refrigerate for at least 2 hours, preferably overnight.
  2. Step 2: Preheat your grill to medium-high heat (about 450°F). While the grill heats, prepare the charred scallion salsa by placing 6 whole scallions directly on the grill grates. Grill for 3-4 minutes per side until the scallions are slightly blackened and softened.
  3. Step 3: Remove scallions from the grill and chop them finely. In a small bowl, mix chopped scallions with 1 tbsp fresh lime juice and 1/2 tsp red chili flakes. Set aside.
  4. Step 4: Remove the flank steak from the marinade, letting excess drip off. Grill the steak over direct heat for 4-5 minutes per side for medium-rare, or longer to desired doneness. Let the steak rest for 5 minutes before slicing against the grain.
  5. Step 5: Slice the steak thinly and spoon the charred scallion salsa over the top. Serve immediately.

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Frequently asked questions

How long does Grilled Mustard-Marinated Flank Steak with Charred Scallion Salsa take to make?

Total time is about 30 minutes (15 min prep + 15 min cook). A small batch typically covers several meals in the week — store as the recipe directs.

How do I store leftover Grilled Mustard-Marinated Flank Steak with Charred Scallion Salsa?

Transfer to an airtight jar and refrigerate for up to 5–7 days. Most sauces freeze well for up to 2 months — portion into small containers or freezer bags so you can thaw only what you need. Stir before serving; cream- or yogurt-based sauces may separate on standing.

Can I substitute ingredients in Grilled Mustard-Marinated Flank Steak with Charred Scallion Salsa?

Yes — most ingredients in this recipe have flexible swaps. For oil, use any neutral high-smoke-point oil (avocado, grapeseed, refined coconut). For aromatics, dried herbs at ⅓ the volume of fresh work in a pinch. The full ingredient list is shoppable on Instacart so you can see substitutes in real time.

How do I scale Grilled Mustard-Marinated Flank Steak with Charred Scallion Salsa for a different number of people?

The recipe is written for 4 servings. Multiply each ingredient by (your serving target / 4). Cook time stays roughly the same up to 2x; for 3-4x batches, switch from a skillet to a sheet pan or stockpot so the food isn't crowded — overcrowding steams instead of browns.

What goes well with Grilled Mustard-Marinated Flank Steak with Charred Scallion Salsa?

American beef like this pair well with a simple grain (rice, couscous, or crusty bread), a quick salad with acid (lemon vinaigrette, pickled onions), and a pan sauce or yogurt-based dip. Tap "Plan a meal with the AI" to get specific side suggestions.

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