In bowl, beat egg lightly; mix in onion, crumbs, garlic, Parmesan, oregano, salt and pepper. Mix in turkey. Shape heaping tablespoonfuls into balls.
In large skillet, heat oil over medium-high heat; cook meatballs, in batches if necessary, for 8-10 minutes or until browned on all sides. Transfer to paper towel-lined plate.
Add onion, garlic, mushrooms, green pepper, basil, sugar, oregano, salt, pepper and 2 tb water to skillet; cook over medium heat, stirring occasionally, for about 10 minutes or until vegetables are softened. Stir in tomatoes and tomato paste; bring to boil. Add meatballs; reduce heat and simmer for 30 minutes or until slightly thickened.
Meanwhile, in large pot of boiling salted water, cook rigatoni for about 8 minutes or until pasta is tender but firm. Drain and return to pot; add tomato sauce, stirring to coat rigatoni.
Transfer to 11x7-inch baking dish or 8-cup shallow oven casserole. Sprinkle mozzarella (use part-skim mozzarella), then Parmesan evenly over top.
Bake in 400ºF oven for about 20 minutes or until cheese is melted and top is golden.