Prepare the Oven & Baking Dish: Preheat your oven to 375°F (190°C). Grease a 9x13-inch baking dish with cooking spray or butter.
Prep the Hashbrowns: In a large bowl, toss the shredded hashbrowns with the melted butter (or olive oil) and a pinch of salt and pepper. Spread the hashbrowns evenly in the bottom of the prepared baking dish.
Cook the Sausage: In a skillet, cook the sausage over medium heat until browned and fully cooked. Drain any excess grease. Add the diced bell pepper and onion, cooking for an additional 3-4 minutes until softened.
Prepare the Egg Mixture: In a separate bowl, whisk together the eggs, milk, salt, and pepper. Add in 1 cup of shredded cheese, and mix until fully combined.
Assemble the Casserole: Evenly distribute the sausage and vegetable mixture over the hashbrowns. Pour the egg mixture over the top, spreading it out to cover everything. Sprinkle the remaining ½ cup of shredded cheese over the casserole.
Bake: Place the casserole in the preheated oven and bake for 40-45 minutes, or until the eggs are fully set and the top is golden brown.
Serve: Let the casserole cool for a few minutes before slicing into 8 servings. Garnish with chopped parsley, if desired.