Preheat the oven to 350°F.
Lightly grease a 9x13-inch baking dish.
In a large skillet over medium heat, cook the breakfast sausage until it is no longer pink.
Break the sausage into crumbles as it cooks.
Drain any excess fat from the skillet.
Add the room-temperature cream cheese to the cooked sausage.
Stir until the sausage and cream cheese are fully combined.
Transfer the sausage and cream cheese mixture to a bowl and set aside.
Add the frozen shredded hash browns to the skillet.
Cook the hash browns until lightly browned.
Spread the lightly browned hash browns evenly in the bottom of the prepared baking dish.
Spoon the sausage and cream cheese mixture evenly over the hash browns.
Sprinkle the shredded cheddar cheese evenly over the sausage mixture.
In a large bowl, whisk together the eggs, salt, black pepper, garlic powder, onion powder, and milk.
Whisk until the egg mixture is fully combined and smooth.
Pour the egg mixture evenly over the hash brown, sausage, cream cheese, and cheddar layers.
If baking later, cover the dish tightly and refrigerate until ready to bake.
Bake the casserole, uncovered, for 40 to 50 minutes, or until the eggs are fully set and the center is no longer jiggly.
Remove the casserole from the oven.
Allow the casserole to rest for 5 to 10 minutes before slicing.
Serve warm.