Feel free to add other vegetables you like, such as mushrooms or spinach. For a spicier version, add some chopped chili or cayenne pepper to the filling. If you prefer, use a different type of cheese, like feta or cheddar. Leftover stuffed peppers can be stored in an airtight container in the fridge for up to 2 days. Reheat in the oven at low temperature until heated through.