Preparation / Directions:
Place sliced beef in 2 tablespoons soy sauce to marinate.
Heat 1 tablespoon oil in wok until hot. Add onions and green pepper and stir fry for 5 minutes. Remove from wok.
Add 2 tablespoons oil to wok. Add beef and cook until brown, about 5 minutes. Remove from wok.
Mix together brown sugar and cornstarch. Stir in vinegar, reserved pineapple juice and 1 tablespoon soy sauce until smooth. Pour into wok; cook over medium heat, stirring constantly, until mixture thickens and boils. Boil and stir 1 minute.
Add meat, pineapple, green peppers and walnuts. Heat through.
Serve over hot cooked rice.