POUR 1/4 cup steak sauce over steak in shallow dish; turn to evenly coat steak. Refrigerate 30 min. to marinate. Meanwhile, mix remaining steak sauce and sour cream until well blended. Refrigerate until ready to use.
HEAT grill to medium heat. Remove steak from marinade; discard marinade. Grill steak 16 to 18 min. or until medium doneness, turning occasionally.
CUT steak across the grain into thin slices; top with sauce. Serve with rice.