Place the chicken in a large resealable plastic bag.

Add barbecue sauce.

Seal the bag and turn to coat.

Refrigerate overnight.

Grill chicken, covered, over medium hot heat for 6 to 8 minutes on each side or until a meat thermometer reads 170°.

Cool.

Cover and refrigerate chicken until chilled.

Chop chicken.

Place in a large bowl.

Stir in the mayonnaise, onion, celery, salt and pepper flakes.

Serve on rolls with lettuce and tomato.