Make Sausage and Vegetables: Cook the sausage in a pan until it is brown and crumbled. Cook the onions and bell pepper (if using) in the same pan until they are soft.
Put the cooked sausage in a greased pie dish. Put the cooked vegetables and grated cheeses on top.
Make the egg mixture by mixing the eggs, milk, flour, baking powder, salt, and pepper together.
Pour the beaten eggs over the sausage and cheese in the baking dish.
Cook the pie in a hot oven at 350°F (175°C) for 35-40 minutes, or until it is firm.
Serve: Allow the pie to cool a bit before serving. Add green onions or chives on top if you like.