MIX marinade, peanut butter, ginger, lime zest and juice with wire whisk until well blended. Reserve 1/4 cup of the marinade mixture to serve with the cooked steak.
PLACE steaks in resealable plastic bag. Pour 1/2 cup of the marinade mixture over steaks; seal bag. Turn over several times to evenly coat steak. Refrigerate 30 minutes to marinate. Remove steaks from marinade; discard marinade.
PREHEAT grill to medium heat. Grille steaks 4 to 6 minutes on each side for medium rare (145°F) to medium doneness (160°F), brushing frequently with the remaining marinade mixture. Cut each steak in half. Serve with the 1/4 cup reserved marinade mixture.