rinse meat under cold water and place in plastic ziploc bag.
Put salad dressing, onion, and spices in bag with meat and seal the bag. Toss back and forth to mix ingredients. Place in fridge for at least one hour. (I like to leave mine overnight or 24 hours for fuller flavor)
Heat grill to about 350 to 400 deg. Cooking serface should be 6 to 8 inches from heat sorce. Remove meat from bag and place on grill, close lid. Let grill 5 min. Turn meat 1/4 turn, leave for 5 more min. Turn meat over, grill 5 min. turn 1/4 turn grill 5 more min. Remove from grill and place on plate. Cover plate with foil and let stand 5 min. London broil should be pink in middle by placeing on plate and covering with foil, the jucies that run out will return to meat and finish heating center of meat.