Heat oven to 350°F; grease a 9-by-13-inch baking dish.

Squeeze thawed hash browns firmly in a clean towel until very little water drips out.

Mix potatoes, 1 1/2 cups cheddar, soup, sour cream, butter, onion, salt, and pepper until evenly coated.

Spread loosely in dish; top with remaining 1/2 cup cheddar.

Bake 45 to 50 minutes until center bubbles and edges brown. Rest 10 minutes.