Preheat your oven to 350°F (175°C).
In a skillet over medium heat, cook the bacon until crispy. Remove and drain on paper towels, then chop.
In a large bowl, combine the hashbrowns, bacon, cheddar cheese, and onion.
In a separate bowl, mix together the milk, beaten eggs, salt, and pepper.
Pour the milk and egg mixture over the hashbrown mixture and stir to combine.
Pour the combined mixture into a greased 9x13 inch baking dish.
Bake in the preheated oven for about 1 hour, or until the top is golden brown and the casserole is set.
Let it cool for a few minutes before serving. Enjoy!