You can make this the evening before and just toss it in the oven come morning.
In a small greased 11 X 7 inch pan or divide between two small greased ramekins put croutons on bottom; add the sausage then the mushrooms, onion, green pepper and cheddar cheese. Beat eggs and milk together and then pour over the rest of the ingredients. depending on the size of you casserole dish you may not use all of the egg mixture. Make sure the mixture does not go over the top of the cheese. You want it to stop about a quarter inch below the top of your casserole.
Refrigerate covered overnight or two hours in the fridge.
Preheat oven to 325. And bake for 40 to 50 minutes until toothpick comes out clean.