Step 1

Line a slow cooker with a slow cooker liner or spray with cooking spray.

Step 2

Melt butter in a skillet over medium heat and cook onion until soft and translucent, 5 to 6 minutes.

Step 3

Place onion, hash browns, mushroom soup, 1 1/2 cups Cheddar cheese, sour cream, garlic powder, salt, and pepper in the slow cooker. Stir until well combined.

Step 4

Cook on High until hash browns are tender, 2 1/2 to 3 hours. Top with remaining 1/2 cup Cheddar cheese and cook until cheese is melted, 15 to 20 minutes. Top with green onions.