Add sausage to a large skillet and heat over medium-high heat until browned. Drain excess grease if necessary.
Add flour and mix well.
Stir in milk and season with salt and pepper. Heat flour and sausage mixture over medium-high heat until mixture is thick and bubbly.
Remove skillet from heat and set aside.
In a separate skillet, cook hash brown potatoes according to package directions. Remove from heat.
Preheat the oven to 375 and grease a 9x13 baking pan with nonstick cooking spray.
Spread cooked hash brown potatoes into the bottom of the pan.
Add quartered biscuits on top of potatoes and 1-1/2 cups shredded cheese.
Gently pour the egg mixture on top, evenly distributing throughout the pan.
Top with homemade sausage gravy and the remaining 1/2 cup cheese.
Bake breakfast casserole for 35-45 minutes or until bubbly and the center comes out clean when a knife is inserted.
Let Sunday Breakfast Casserole stand for a few minutes before serving hot.
Notes
Topping IdeasBreakfast casserole can be served with green onions or additional green bell pepper to add color to the dish. Some may want a side of hot sauce or sour cream.