Grape-Nuts is a breakfast cereal developed by C. W. Post in 1897. Post was a patient and later competitor of the 19th-century breakfast food innovator, Dr. John Harvey Kellogg. Despite its name, neither grapes nor nuts have ever been ingredients in the cereal. The cereal is actually made from wheat and barley. Mr. Post believed that sucrose (which he called "grape sugar") formed during the baking process. This, combined with the nutty flavor of the cereal, inspired its name. Another explanation originates from employees at Post, who claim that the cereal got its name due to its resemblance to grape seeds, or grape "nuts."

Grape-Nuts was initially marketed as a natural cereal that could enhance health and vitality, and also as a "brain food." Its lightweight and compact nature, nutritional value, and resistance to spoilage made it a popular food for exploration and expedition groups in the 1920s and 1930s. Just before World War II, Grape-Nuts was included as a component of the lightweight Jungle ration used by some U.S. and Allied forces in wartime operations before 1944.Kearny, Cresson H. (Major), Jungle Snafus...And Remedies, Oregon Institute (1996), pp. 290-291

During the 1960s, advertising for the brand promoted Grape-Nuts as the cereal that "fills you up, not out." Brand users, particularly mother/daughter look-alikes, were shown engaged in fitness activities such as tennis, horseback riding, skiing, and swimming.

This ad campaign produced at least one television commercial featuring a "catch-phrase" that became a target for numerous sketches, comics, riffs, and take-offs in other media. Spanning the ensuing two decades, "Oh no, Mrs. Burke! I thought you were Dale!" was parodied in the film The Kentucky Fried Movie and continued to appear in comedy. This line is remembered most today by those who saw the 1968 through 1970 commercial, and has also become familiar to many too young to have seen the original TV spots.

A subsequent ad campaign utilized a similarly catchy phrase, as Euell Gibbons became the spokesperson for the brand, promoting Grape-Nuts as the "Back to Nature Cereal." The line "Ever eat a pine tree?" proved to draw increased attention to the product from consumers, as well as from comedians of all sorts.

Grape-Nuts is credited with being the first widespread product to use a coupon in sales promotion when C.W. Post Company offered a penny-off coupon to get people to try their cereal in the late 1890s.

At one time, Grape-Nuts was the seventh most popular cold cereal, but sales declined as Post was sold from one company to another. Circa 2005 it held less than 1% of the market. About this time the formula was changed, grinding the grain husks into the flour so it could be pitched as "whole grain." The addition of vitamins and minerals allowed it to qualify for food-stamp programs.Newman, B., Wall Steet Journal, June 1, 2009 Ralcorp, the current owner of Post, has undertaken new advertising campaigns to try to revitalize sales of the Post cereals.Vranica, S., Wall Street Journal, March 26, 2009