Preheat oven to 350°F. Grease a 2-quart baking dish with cooking spray or butter.
In a large mixing bowl, combine cream of mushroom soup, milk, garlic powder, salt, and pepper, stirring until smooth and well blended.
Add the drained green beans, shredded cheddar cheese, and half of the French fried onions to the soup mixture. Stir gently until everything is evenly coated.
Pour the green bean mixture into the prepared baking dish and spread evenly.
Bake uncovered for 25 minutes until the casserole is hot and bubbly around the edges.
Remove from oven and sprinkle the remaining French fried onions evenly over the top. Return to oven and bake for an additional 5 minutes until onions are golden and crispy. Serve hot.