MIX barbecue sauce, lime juice, tequila, chipotle peppers, garlic salt and cayenne pepper in large resealable plastic bag. Add chicken; seal bag. Turn bag over several times to evenly coat chicken with the barbecue sauce mixture. Refrigerate 30 min. to marinate.
PREHEAT oven to 450ºF. Remove chicken from marinade; discard bag and marinade. Place chicken in single layer in shallow foil-lined baking pan.
BAKE 15 min. or until chicken is cooked through. Serve topped with the onions.