Crumble breads, add all other ingredients except butter. (You may want to cook the celery and onions to just tender before adding to other ingredients, My mom pops them into the microwave for a minute or two.)
Spray crockpot with cooking spray. Pour mixture into crockpot and cover.
Cook on high for 2 hours or on low for 3 to 4 hours.
Stir in cooked chicken about an hour before dressing is finished cooking.