Preheat oven to 400 degrees F.
Slice tops off peppers, remove seeds and trim ribs, if necessary. Place peppers in a baking dish and add about 1-inch of water. Cover with foil and bake in preheated oven for 20 minutes, until slightly tender. Remove from oven and reduce oven temperature to 375 degrees F. Remove the peppers from baking dish and pour off the water. Return the peppers to the empty baking dish.
While peppers are in the oven, add 1 tablespoon vegetable oil to a large saute pan and place over MEDIUM-HIGH heat. Add the ground beef and cook, stirring to break up the beef, until browned and cooked through. Drain off as much grease as possible from the pan.
Return the pan to MEDIUM heat, add the onion and garlic and cook until tender. Add the taco seasoning, tomatoes, tomato sauce, beans, rice, green chiles, frozen corn, crushed red pepper (if using), and 1 cup of the cheese. Cook until combined and cheese has melted.
Fill the peppers with the beef mixture, packing it down and mounding it slightly. Cover the baking dish with foil and bake at 375 degrees F for 25 minutes to 30 minutes, or until the peppers are very tender and the filling is heated through.
Remove the foil, top with remaining shredded cheese, and bake for an additional 5 minutes until cheese has melted.