Pierce pork chops with a fork several times on each side. Combine pork chops and next 3 ingredients in a large shallow dish or large zip-top plastic freezer bag. Cover or seal, and chill for 30 minutes.
Remove chops from marinade, discarding marinade. Sprinkle chops evenly with salt and black pepper.
Stir together marmalade and barbecue sauce in a small bowl. Brush one side of pork chops evenly with half of marmalade mixture.
Grill chops, marmalade mixture side up and covered with grill lid, over medium-high heat (350° to 400°) 10 minutes. Turn pork chops, and brush evenly with remaining half of marmalade mixture. Grill 10 minutes or until done. Remove chops from grill, and let stand 5 minutes.
Grill orange slices, covered with grill lid, over medium-high heat 1 minute on each side. Serve with pork chops.
*4 (1 1/4-inch-thick) boneless pork loin chops may be substituted. Reduce grilling time to 8 minutes on each side or until done.
Note: For testing purposes only, we used Jack Daniel's Original No. 7 Barbecue Recipe Grilling Sauce.