Sauce: In bowl stir together soy sauce, orange juice, cornstarch, sugar and, if desired, red pepper. Set aside. Rinse chicken and pat dry. Cut into 1-inch pieces; set aside.
Preheat wok or large skillet over high heat; add oil. (Add more oil as necessary during cooking.) Stir-fry peanuts in hot oil about 1 minute or until lightly toasted. Remove from wok or skillet. Add gingerroot; stir-fry 15 seconds. Add green peppers and green onions; stir-fry about 3 minutes or until crisp-tender. Remove vegetables from wok or skillet.
Add chicken to wok or skillet; stir-fry 2 to 3 minutes or until no longer pink. Push chicken from center or wok. Stir sauce; add to center of wok. Cook and stir until thickened and bubbly. Stir in peanuts and vegetables; cook and stir 1 to 2 minutes more or until heated through. Serve with hot rice. Stir in oranges just before serving.