Preheat oven to 350 degrees Fahrenheit.
Cook pasta according to instructions on package. Set aside.
Cook ground beef and diced green peppers together until beef is browned.
Mix ground beef mixture, sauce, Italian seasoning, garlic powder, canned mushrooms, and pasta together in a large bowl.
Pour into a 9 x 13 casserole dish.
Cover with foil and bake for 20 minutes.
After 20 minutes take it out and sprinkle cheese and put sliced pepperoni on top of the pasta. Bake uncovered for another 15 minutes.
Take it out and let it sit to cool for about 10 minutes.
Serve with homemade bread for a perfect dinner!