1 beef flank steak (about 2 lbs.)
4 oz. onion, minced
1 clove crushed garlic
2 tbsp. vinegar
2 tbsp. mustard
1 tbsp. Worcestershire sauce
1 tsp. salt
1/2 tsp. pepper

Combine all ingredients except meat. Spread evenly both side of beef. Wrap in foil, let marinate for 1 hour. Grill over barbecue 10-15 minutes each side; as it grills, brush with marinade. Cut vertically against grain when serving.