Preheat the oven to 400 F. Prep the casserole dish. Melt 1 tablespoon of butter and use a silicon brush to coat the inside of the casserole dish. Set aside.
Bake the bacon: While the oven is preheating, line a baking sheet with parchment paper and place 8 ounces of bacon strips side by side on the pan. Place the baking sheet in the oven on the middle rack. Bake around 15 minutes. Check the bacon often to make sure it does not overcook.
Cook the filling: Cook the sausage in a stove top pan. Place the cooked sausage in the casserole dish. Remove any excess sausage grease from the pan and then sauté the diced onion, peppers and garlic in the remaining grease. When perfectly sautéd with light browning, place in the casserole dish.
Remove the bacon from the oven and allow to cool before handling.
Assemble the casserole: Top the sausage and veggies with cheese. After the bacon has cooled, crumble into the casserole dish and mix all the ingredients together until well distributed.
Whisk the eggs and milk together. Pour the egg mixture over the meat and veggies and lightly mix with a wooden spoon or spatula.
Add a bit of salt and pepper and green onion slices on top.
Place the casserole dish in the oven, on the middle rack, and bake for 25-30 minutes.
Once baking is complete, remove from the oven and allow to cool for 5 minutes before serving.