Barbecued London Broil
["1 (3 to 3 1/2 lb.) top round London Broil", "1/2 c. each: water and olive oil", "1/4 c. ketchup", "1/3 c. red wine vinegar", "1/4 c. minced onion", "2 large cloves garlic, minced", "1 Tbsp. Worcestershire sauce", "1 tsp. salt", "1/2 tsp. dry mustard", "1/4 tsp. dried red pepper flakes", "1/4 tsp. black pepper"]
["Combine marinade ingredients; pour over meat in large plastic container or plastic marinating bag.", "Refrigerate, turning occasionally, at least 8 hours or overnight.", "When grill is ready, remove meat and pat dry, reserving marinade.", "Grill according to desired doneness, about 25 minutes for rare.", "Place reserved marinade in small saucepan and bring to a boil.", "Reduce heat and simmer about 5 minutes or until slightly thickened.", "Skim any oil from the top and serve with the meat that has been sliced thin diagonally across the grain."]
["Broil", "water", "ketchup", "red wine vinegar", "onion", "garlic", "Worcestershire sauce", "salt", "dry mustard", "red pepper", "black pepper"]