DO-AHEAD TIP: Marinate halibut and fruit and vegetables for 4 to 6 hours (see recipe). If using bamboo skewers, soak them in water for 30 minutes before use, to prevent burning.
In a medium bowl, whisk together the first 7 ingredients (wine/juice through black pepper); blend well then pour half of the mixture into a large zipper-topped plastic bag; add halibut, seal bag and turn to coat.
Pour remaining marinade into another large zipper-topped plastic bag; add red onion, apple and bell pepper pieces, seal bag and turn to coat.
Refrigerate both bags for 4 to 6 hours, turning occasionally.
Preheat oven broiler. Drain fish, discarding marinade. Drain fruit and vegetables, reserving marinade for basting.
Alternately thread fish, onion, apple and bell pepper onto skewers; broil 4 to 6 inches from heat source for 2 to 3 minutes per side or until fish flakes easily when tested with a fork and fruit and vegetables are tender.
Baste frequently with reserved marinade.