PLACE onions, carrots and celery in slow cooker; top with chicken.
ADD combined brown sugar, dressing, soy sauce and ginger. Cover with lid.
COOK on LOW for 7 to 8 hours (or on HIGH for 3-1/2 to 4 hours). During last 30 min. of cooking time, increase to HIGH. Stir cornstarch into reserved pineapple liquid; add to slow cooker along with the pineapple and peppers. Cook 30 min. or until peppers are crisp-tender and sauce is thickened. Serve over the rice.