In a large skillet or wok, stir-fry chicken in oil for 7 minutes or until juices run clear; remove and set aside. In the same skillet, stir-fry onion until tender. Add broccoli, green pepper and garlic; stir-fry until tender. In a small bowl, combine remaining ingredients until smooth; pour over vegetable mixture. Add chicken; bring to a boil. Cook and stir for 1 minute or until sauce is thickened and bubbly.