Combine dressing, sherry, onion, Worcestershire, and pepper.
Pour over meat in shallow dish.
Marinate, covered, at room temperature several hours or refrigerate overnight, turning at least once and spooning sauce over occasionally.
Drain, reserving marinade.
Broil meat over hot coals for 40 to 50 minutes, turning every 10 to 15 minutes and brushing with marinade.
Meat will be rare; cook longer for desired doneness.