My husband has been grilling London Broil's for a long time ... he first learned how from his father many years ago. Over the years, he's tried many different marinades, some good, and some not so good. After awhile, he decided to make his own and oh my goodness, it is awesome! Feel free to adjust all seasonings to your taste.
1/3 cup oil
1 tbls. red cooking wine
1 tbls. balsamic vinegar
1 tbls. minced garlic
1/2 tsp. ground white pepper
1/4 tsp. thyme leaves
1 1/2 tsp. Worcestershire sauce
1 1/2 tsp. course-ground black pepper
1/8 tsp. onion powder
1 London Broil (top round roast)
Pierce London Broil all over with the tines of a fork. Mix marinade in a zip-top bag, seal and shake to blend all. Add London Broil and marinade several hours (or overnight) in your refrigerator, turning from time to time to evenly soak meat in marinade.
Grill on sear burner 1 minute per side; continue to grill on direct high about 5-7 minutes per side depending on thickness. Remove, cover with foil and let rest 5 minutes before slicing/serving.