• In a large bowl, whisk together all of the marinade ingredients until completely combined. Pour marinade into a large zip-top plastic bag. Add London Broil to the bag, squeeze out all of the air, and seal the bag. Toss gently to coat the London Broil with the marinade.
  
• Place in refrigerator to marinate for about 4 hours (or up to 2 days), tossing occasionally to redistribute marinade.
• Remove meat from the marinade, discard the marinade, and pat the meat dry.

TO GRILL:

• Allow the meat to sit on the counter for about 30 minutes to come to room temperature. Remove meat from marinade and grill the meat for about 4 minutes per side over direct heat, then move to indirect heat until the meat reaches 125-130°F for rare, 135°F for medium-rare, or 145°F for medium. Transfer meat to a cutting board and let stand 10 minutes. Cut meat diagonally across the grain into thin slices.
  

TO BROIL:

• Allow the meat and marinade to sit on the counter for about 30 minutes to come to room temperature. Meanwhile, preheat the broiler and the broiler pan to HIGH. Allow to heat for 10 minutes.
• Make sure to use an actual broiler pan, rather than a baking pan. A broiler pan has a rack built in that prevents the rendered fat from becoming a fire hazard. Transfer the meat to the broiler pan and discard the marinade in the bag. 
• Broil the steak for 8 to 12 minutes, turning once about halfway through. The specific time will vary depending on the size and thickness of your steak, so use an instant-read thermometer to know when your meat is done. It should be 125-130°F for rare, 135°F for medium-rare, or 145°F for medium. Transfer meat to a cutting board and let stand 10 minutes. Cut meat diagonally across the grain into thin slices.