Preheat barbecue on HIGH. Brush the grids with vegetable oil. Place pork on hot grids, and reduce heat to MEDIUM – LOW, and grill, turning every 5 minutes to sear each side, for a total cooking time of about 20 minutes. Let stand 5 minutes to reabsorb juices, then slice into medallions.
Meanwhile, place the reserved marinade in a saucepan on the sideburner, and heat to boiling. Boil until slightly reduced, about 5 minutes. Serve alongside the tenderloin.