In a large bowl, whisk together the 2 cans of cream of mushroom, milk, salt, pepper, and onion powder. Then stir in the browned meat, shredded hash browns and green beans.
Spray a 6-quart slow cooker with non-stick spray. Add the mixture you just made into the slow cooker, and gently flatten it.
Cover and cook on LOW for 4 hours, without opening the lid during the cooking time.
During the last 15 minutes add the shredded cheese. Cover and let the cheese melt.