Pat the London broil dry
Trim excess fat and silver skin
Marinate for 4 to 24 hours
Preheat grill to high heat
Oil the grill grates
Remove the steak from the marinade
Let excess marinade drip off
Season lightly with salt and pepper if desired
Place the steak on the hot grill
Grill for 4 to 6 minutes per side for medium-rare
Flip only once
Check for doneness with a meat thermometer
Remove at 125 to 130°F for medium-rare
Remove at 135 to 140°F for medium
Transfer to a cutting board
Rest for 10 to 15 minutes
Slice thinly against the grain
Serve immediately