- Cut tofu into 1/2-inch cubes; drain on several layers of paper towels 10 minutes.
- Meanwhile, cut chicken into 1/2-inch cubes. Combine cornstarch, soy sauce and sugar in bowl; stir in chicken. Let stand 15 minutes.
- Heat 1 Tbsp. oil in hot wok or large skillet over high heat. Add chicken and stir-fry 3 minutes; remove.
- Heat remaining 1 Tbsp. oil in same pan. Add onion and green pepper; stir-fry 3 minutes.
- Add chicken and sweet & sour sauce; reduce heat to medium. Cook and stir 1 minute. Gently stir in tofu and oranges; cook until heated through.