Preheat oven to 375°F (190°C) and grease a 9x13 inch baking dish with non-stick cooking spray.
In a large skillet over medium-high heat, brown the ground sausage until fully cooked and no pink remains. Drain excess fat thoroughly.
In a large mixing bowl, whisk together the eggs, milk, salt, black pepper, garlic powder, and onion powder until the mixture is homogeneous.
Spread the thawed hash browns evenly across the bottom of the prepared baking dish in a uniform layer.
Distribute the cooked sausage over the hash brown layer and sprinkle the shredded cheddar cheese evenly over the top.
Pour the egg and milk mixture slowly and evenly over the layers to ensure complete coverage.
Bake for 40 to 45 minutes until the center is set and the top is golden brown.
Remove from the oven and allow the casserole to rest for 10 minutes before slicing to ensure the structure is firm.