DO-AHEAD TIP: Marinate London broil overnight or for at least 4 hours (see recipe).
Place London broil in a large zipper-topped plastic bag. In a food processor, combine remaining ingredients (basil through olive oil); blend until smooth then pour mixture over beef.
Seal bag and turn several times to completely coat beef. Refrigerate overnight or for at least 4 hours.
At time of cooking, preheat outdoor grill to MEDIUM-HIGH. Remove London broil from marinade (reserving marinade in a bowl); grill for 14 to 20 minutes (the general rule is 7 minutes per pound for a nice medium-rare).
Rotate beef every 4 to 5 minutes and brush with marinade. Allow London broil to sit for 10 minutes then thinly slice against the grain (diagonally) and serve!