While rice is cooking, heat oil in large nonstick skillet over medium-high heat until hot. Add onions and carrots; cook 5 minutes, stirring occasionally. Add celery and bell pepper; cook and stir 3 minutes.
Stir in chicken, pineapple and sweet and sour sauce. Bring to a boil. Boil gently 5 minutes or until chicken is no longer pink, stirring occasionally. Serve over rice.