Fold four 18x15-in. pieces of heavy-duty aluminum foil in half; fold up edges to make pans about 12x7 in. Place four strips of bacon in each foil pan; top each with a fillet and 1/4 cup onion. Drizzle with butter and honey. Sprinkle with salt and pepper.
Grill, covered, over medium heat 12-15 minutes or until fish flakes easily with a fork. Open foil carefully to allow steam to escape. Cut fillets in half; serve each with two bacon strips.