"Where's the beef?" is a catchphrase in the United States and Canada, introduced as a slogan for the fast food chain Wendy's in 1984. Since then it has become an all-purpose phrase questioning the substance of an idea, event, or product. The phrase first came to the public audience in a U.S. television commercial for Wendy's chain of hamburger restaurants in 1984. The strategy behind the campaign was to distinguish competitors' (McDonald's and Burger King) big-name hamburgers (Big Mac and Whopper respectively) from Wendy's "modest" Single by focusing on the large bun used by the competitors and the larger beef patty in Wendy's hamburger.

Source: Wikipedia