Prepare the Green Beans

1. Cook the Green Beans: If using fresh beans, trim the ends and blanch them in boiling water for about 5 minutes, then drain. If using canned beans, just drain and rinse them.

Make the Casserole

1. Mix the Casserole Base: In a large bowl, combine the cream of mushroom soup, milk, garlic powder, onion powder, salt, and pepper. Stir until smooth.
2. Add the Green Beans: Add the green beans to the soup mixture and stir until well coated.
3. Transfer to Baking Dish: Pour the green bean mixture into a greased 9×9-inch baking dish or a similar-sized casserole dish.

Top and Bake

1. Add Fried Onions: Sprinkle the fried onions over the top of the casserole.
2. Bake: Place the casserole in a preheated oven at 350°F (175°C) and bake for 25-30 minutes, or until the casserole is bubbly and the topping is golden brown.
3. Cool Slightly: Remove from the oven and let it cool for a few minutes before serving.