Heat oven to 350°F. Cook pasta as directed on package; drain.
In ungreased 3-quart casserole or 13x9-inch (3-quart) glass baking dish, place pasta. Stir in peppers, tomatoes, shrimp, tomato sauce, mushrooms, oregano and red pepper flakes; sprinkle with cheese. Cover with foil.
Bake 15 to 20 minutes or until thoroughly heated.