Green Bean Casserole is very simple to make. All you need is a can of mushroom soup, 1/2 cup of milk, 4 cups of green beans, 1 1/4 cup of French fried onions, and a little salt and pepper. Combine everything, except for 1/2 of the French fried onions, in a casserole dish, and put it in the oven for 25 minutes on 350 degrees. Take it out and put the other half of the French fried onions on top of it, and cook for an additional 5 minutes. Remove from the oven and serve.