Spray a 9x13 pan with cooking spray and set aside.
In a large bowl, combine the thawed hash browns,melted butter, cream of chicken soup, sour cream, chopped onion, shredded cheddar, salt, and pepper. Mix thoroughly until everything is evenly combined.
Pour the mixture into your prepared 9x13 pan and spread evenly.
Bake for 45 minutes until cooked all the way through and the top starts to brown.