Grilled Mustard-Marinated Flank Steak with Charred Scallions

By AislePrompt Editorial · Published 2026-06-14 · Updated 2026-06-14

How this recipe was made — this recipe was drafted by AislePrompt's AI-assisted pipeline from technique templates and USDA-sourced nutrition data, and published by AislePrompt Editorial — see how AislePrompt recipes are developed and reviewed.

A smoky grilled flank steak marinated in tangy Dijon mustard and herbs, served alongside sweet charred scallions for a hearty summer main. This American-inspired barbecue recipe, ready in about 30 minutes, pairs flank steak, Dijon mustard, olive oil for a weeknight-friendly dinner that comes together with one pan and minimal cleanup. Each serving lands at about 380 calories and feeds 4, so it slots cleanly into a weekly meal plan and pairs well with a quick salad or grain on the side. 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 380 cal/serving

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Ingredients

1.5 pounds flank steak
3 tbsp Dijon mustard
2 tbsp olive oil
3 garlic cloves, minced
1 tbsp fresh thyme leaves
1 tsp salt
1 tsp black pepper
8 whole scallions
1 tbsp lemon juice

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Instructions

Step 1: In a medium bowl, whisk together 3 tablespoons Dijon mustard, 2 tablespoons olive oil, 3 minced garlic cloves, 1 tablespoon fresh thyme leaves, 1 teaspoon salt, and 1 teaspoon black pepper to create a marinade.
Step 2: Place 1.5 pounds flank steak in a large resealable plastic bag and pour the marinade over it, massaging to coat thoroughly. Refrigerate and marinate for at least 2 hours or overnight.
Step 3: Preheat grill to medium-high heat (about 400°F). Remove steak from marinade and let excess drip off.
Step 4: Grill the flank steak for 4-5 minutes per side until medium-rare (internal temperature 130-135°F), turning once. Remove and let rest for 10 minutes.
Step 5: While steak rests, place 8 whole scallions on the grill and cook for 3-4 minutes per side until tender and charred, turning occasionally.
Step 6: Slice the steak thinly against the grain and drizzle with 1 tablespoon lemon juice. Serve with charred scallions alongside.