Brown and drain sausage (can be done the night before).
Spread bottom of casserole dish with butter.
Place 1/2 of the cheese in the dish.
Break eggs in the dish, breaking yolks, and spread evenly over the cheese.
Layer the mushrooms and green pepper over the eggs.
Pour in half and half. Place sausage on top and add remaining cheese.
Bake uncovered at 350 degrees for 30 to 40 minutes.
Let stand 5 minutes before cutting.