Combine onion, parsley, vinegar, oil, mustard, garlic and thyme.
Place beef chuck shoulder steak in plastic bag; add marinade, spreading evenly over both sides. Close bag securely and marinate in refrigerator 6 to 8 hours (or overnight, if desired), turning at least once.
Pour off marinade; discard. Place steak on rack in broiler pan so surface of meat is 3 to 4-inches from heat. Broil 16 to 18 minutes to doneness desired (rare to medium-rare), turning once. Carve steak into thin slices to serve.
Makes 4 servings.
-- Edited by KY LADY CUTTER on Tuesday 25th of October 2011 10:09:21 PM