1In a 1 gallon zip-lock plastic bag or deep bowl, mix vinegar, oil, mustard, Worcestershire, catsup, soy sauce, garlic and pepper. Add steak and marinate in the refrigerator for at least 4 hours.
2Lift steak from marinade and drain briefly. Reserve marinade.
3Place meat on a grill over medium-hot coals. Cook meat; baste occasionally. Allow 12 to 15 minutes for medium rare steak.
4Transfer meat to a platter and keep warm; pour remaining marinade into a pan and bring to a boil over high heat. Cut meat across the grain into thin, slanting slices, and accompany with the marinade.