Like most American casseroles, this one can trace its roots to the Depression era, which gave rise to a number of one-dish meals that made the best of readily available and inexpensive ingredients. By the end of the Second World War, numerous forerunners of today's classic green bean casserole could be found. A 1947 New York Times article included a recipe for a version made with sliced frankfurters. Another recipe, published in the Los Angeles Times three years later, called for a mixture of green beans, hamburger, condensed tomato soup, and a biscuit topping.

It wasn't until 1955, however, that the dish's most steadfast incarnation entered the scene. This enduring formula, one that many home cooks still use, called for a trinity of convenience products: canned Durkee or French's fried onions, Green Giant canned green beans, and Campbell's condensed cream of mushroom soup, usually accompanied by milk, soy sauce, and a dash of pepper. It was invented by the Campbell's Soup Company, which, as it still does, emblazoned its soup can labels with recipes that featured the company's products in a starring role. According to Cindy Ayers, the vice president of Campbell's Kitchens, the recipe was first tested in order to fulfill a request from Cecily Brownstone, the food editor at the Associated Press, who sought help in reproducing a green bean casserole she'd tasted at a press dinner. "We partnered with a lot of writers back then," Ayers says. "It was a pretty common practice at the time."

The dinner that Brownstone had attended took place at the home of John Snively, a wealthy citrus rancher in Florida, and his wife, May. The conceit of the event was that the Snivelys had served a replica of the evening's menu to Iranian royalty: Shah Mohammed Reza Pahlevi and his wife, Queen Soraya, who had recently paid a visit to the ranch. Mrs. Snively had presented a memorable meal of brunswick stew and a delicious green bean casserole made with cream sauce and mushrooms. The queen, Mrs. Snively told the assembled members of the press, had apparently loved the casserole and "had eaten [it] with gusto". With that, Brownstone had her story and, thanks to some help from the Campbell's Soup test kitchens, her featured dish. The article she wrote was headlined "Beans Fit for an Iranian Queen", and the recipe that ran with it was dubbed "Beans and Stuff", which is how the Snivelys' less than silver-tongued butler had allegedly announced the dish.

Over the years, the Campbell's Soup Company has subtly altered the recipe (which debuted as "Green Bean Bake"), but the basics have remained essentially unchanged. "They tried to create a recipe using ingredients that most consumers had on hand at the time," says Ayers. "No one had any idea that it would turn into the iconic dish that it is today."