Cook the base: Add browned ground beef, corn, soup, sour cream, cheese, onion, garlic powder, salt, and pepper. Stir to combine.
1 pound ground beef, 1 can (15-ounce) corn, 1 can (10.5-ounce) cream of mushroom, 1½ cups shredded cheddar cheese, 1 small onion, 1 teaspoon garlic powder, salt and pepper to taste, ½ cup sour cream