Preheat oven to 375°. In a large bowl, combine all ingredients. Transfer to a greased 13x9-in. baking dish., Cover and bake 30 minutes. Uncover and stir; bake until bubbly and rice and vegetables are tender, 20-25 minutes. If desired, top with chopped green onions., Freeze option: Freeze cooled casserole mixture in freezer containers. To use, partially thaw in refrigerator overnight. Heat in a saucepan, stirring occasionally; add a little water if necessary.