Preheat oven to 350°. In a large skillet, cook beef over medium heat until meat is no longer pink; crumble meat; drain. Stir in the chili powder, oregano, salt and pepper. , In a greased 3-qt. baking dish, layer the rice, beef mixture, mushrooms and green pepper; set aside. In a large saucepan, combine sugar and cornstarch; stir in the remaining sauce ingredients until smooth. Bring to a boil; cook and stir for 2 minutes or until thickened. , Pour sauce over layered ingredients. Bake, uncovered, for 30 minutes or until heated through.