Preheat oven to 350˚F. Spray a 13x9-inch baking dish with nonstick cooking spray.
Line the bottom of prepared baking dish with biscuits.
In a large skillet, cook sausage until browned and crumbly; drain. Sprinkle sausage over biscuit layer and top with 1 cup cheddar cheese.
In a medium bowl, whisk eggs and milk together. Salt and pepper to taste and pour over cheese layer.
Prepare gravy mix according to package directions. Pour gravy over egg layer and sprinkle remaining ½ cup cheddar cheese over casserole.
Bake 30-35 minutes.