1. Brush chops with oil and let stand for about 2 hours at room temperature.
2. Prepare sauce. Heat butter and saute apples and onions. Add ketchup, sugar, salt, and pepper. Bring to a boil. Simmer 3 minutes.
3. Place chops in barbecue sauce and marinate for 30 minutes.
4. Alternate chops and onions on skewers and set over barbecue. Brush remaining sauce on chops and broil about 6 minutes until brown.