Place pork tenderloins in re-sealable plastic bag; set aside. In small bowl, combine marinade ingredients; pour over pork. Seal bag; refrigerate for at least 1 hour to marinate, or up to 24 hours to enhance flavor.
Preheat grill to medium-hot. When ready to grill, remove pork from marinade and place on grill. Cook, covered, for about 10 minutes per side or until the internal temperature of pork is 140°F. Meanwhile, place the pineapple chunks on the skewer; place on grill during the last 6 minutes of grilling time, turning after 3 minutes. To serve, slice pork into 1/2-inch slices (medallions) and serve with grilled pineapple.