¼ c. balsamic vinegar 1 T. Worcestershire sauce 2 tsp. dark brown sugar 1 garlic clove, minced 1 lb. flank steak salt and pepper Combine first four ingredients in a large ziplock bag. Add steak, turn to coat; marinate for 30 minutes at room temperature. Grill until desired doneness. Let stand, covered loosely with foil for 10 minutes, before cutting in thin strips against the grain.