Preheat your oven to 190°C (375°F). Grease a 9x13 inch baking dish.
In a large bowl, whisk together the eggs, milk, salt, and pepper.
Spread half of the thawed hashbrowns evenly in the bottom of the prepared baking dish.
Layer the cooked sausage, chopped onion, and chopped bell pepper over the hashbrowns.
Sprinkle half of the shredded cheddar cheese over the sausage mixture.
Top with the remaining hashbrowns, pressing down gently.
Pour the egg mixture evenly over the entire casserole.
Cover the baking dish with aluminum foil and bake for 30 minutes.
Remove the foil and sprinkle the remaining cheddar cheese over the top. Bake for an additional 20-25 minutes, or until the casserole is set and golden brown.
Let the casserole stand for 5-10 minutes before serving.
Notes
This casserole can be assembled the night before and baked in the morning. For a spicier casserole, add a pinch of red pepper flakes to the egg mixture.