In a large non-stick skillet, heat oil over medium high heat. Season chicken strips and add to pan. Brown chicken and remove to plate. Add red and green peppers and cook for 1 minute. Stir in pineapple chunks, juice, sugar, vinegar and chicken stock and bring to a simmer. Simmer until sauce begins to reduce. Stir in cornstarch mixture and bring liquid to a simmer. Stir in chicken strips and cook for 5 minutes. Serve over rice.