1. Preheat an outdoor grill for medium heat.
2. Place the onion wedges on a sheet of heavy duty aluminum foil. Dot with butter, then sprinkle with bouillon, garlic salt, and pepper to taste. Fold the aluminum foil into a packet, leaving only a small hole at the top to allow steam to escape.
3. Place packet on preheated grill, and cook until the onions have softened, and cooked to a deep, rich brown, 45 minutes to 1 hour depending on the temperature of the grill. Stir the onions after the first 30 minutes, or as needed to keep from burning.