Combine green beans, soup, soy sauce, and half of the onions in a 1 1/2 quart baking dish. Stir to evenly distribute.
Bake until bubbly, about 20-25 minutes. During the last 5 minutes of baking, top with the remaining onions.
Notes
There are lots of variations on this classic. Try topping with 1/2 cup shredded cheese or stirring in a dash of your favorite spices. To make it all the way from scratch, check out our homemade Green Bean Casserole recipe!