Using a sharp knife, cut a 1/2-inch crosshatch pattern, 1/4-inch deep, on both sides of steak.
Place in a 1 gallon ziptop bag.
Place remaining ingredients, EXCEPT black pepper and paprika, in a blender.
Process for 30 seconds and pour into ziptop bag with steak. Turn to coat steak and let sit at room temperature for 2 hours.
Turn all burners on a gas grill to high. Cover and let heat for 15 minutes.
Mix together black pepper and paprika.
Remove steak from marinade and pat dry with paper towels. Season with pepper/paprika mixture.
Place London Broil on grill. Grill for 1 minute and then flip over. Continue to flip every minute until temperature reaches 125 degrees for medium rare or 130 degrees for medium. Total cooking time should be 5 to 9 minutes.