Brown ground beef in a large sauce pan. (I like to use my cast iron pans. Easy clean up!) Drain, remove from pan and set aside. Heat oil in stock pot on medium high heat and add green peppers and onion. Saute 5-10 minutes or until softened, stirring occasionally. To stock pot, add tomatoes, sauce, corn, garlic powder, salt, and pepper. Bring to a boil, then reduce heat and simmer 5 minutes. Stir in rice and ground beef. Pour into a 9×13 baking dish. Top with shredded cheese. Bake at 350 for 12-15 minutes or until cheese is melted.