Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking dish.

In a large mixing bowl, combine thawed frozen shredded hash browns, shredded cheddar cheese, diced onion, diced bell pepper, and crumbled bacon or sausage. Stir until well mixed.

In a separate bowl, whisk together sour cream, melted butter, milk, large eggs, salt, and black pepper until smooth.

Pour the wet mixture over the hash brown mixture and gently fold together.

Spread the combined mixture evenly into the prepared baking dish.

Bake for 45 to 50 minutes until the top is golden brown and the center is set.

Allow the casserole to cool for about 5 minutes before slicing and serving.