1. Place the chicken and onion on a lightly oiled grill rack over medium-hot coals. Grill the chicken uncovered for 15 minutes or until chicken is cooked through, turning and brushing often with the barbecue sauce. Grill the onion for 10 minutes, turning once and brushing with barbecue sauce. Discard any remaining barbecue sauce.
2. Remove the bread from the bag. Separate the bread halves. Top the bottom bread half with the chicken, onion and the remaining bread half. Cut the loaf into quarters. Serve with additional barbecue sauce.
Cooking Basics: Do not peel the onion. Slices will hold together during grilling and the onion peel will burn off.