Balsamic-Marinated Flank Steak Sandwiches with Peppers and Onions | Red Meat Recipes | Weber Grills

Ingredients

• ½ cup/120 milliliters balsamic vinegar
• ¼ cup/60 milliliters extra-virgin olive oil
• 2 tablespoons Worcestershire sauce
• 1 tablespoon Dijon mustard
• 4 garlic cloves, minced or pushed through a press
• 1 teaspoon kosher salt
• ¾ teaspoon freshly ground black pepper
• 1 flank steak, about 1½ pounds and ¾ inch thick
• 2 tablespoons extra-virgin olive oil
• 2 bell peppers, any color, cut into thin strips
• 1 large yellow onion, cut in half and thinly sliced
• ½ teaspoon kosher salt
• ½ teaspoon freshly ground black pepper
• 4 ciabatta or other soft sandwich rolls, split
• 4 teaspoons Dijon mustard