what's the beef? What is the source of a complaint, as in Where's the beef? No one was hurt in the accident. This usage employs beef in the sense of a “complaint” or “grudge,” also appearing in the phrase
have no beef with, meaning “have no quarrel with.”
[ ; late 1800s
Where is the content or substance, as in That was a very articulate speech, but where's the beef? This usage was originally the slogan for a television commercial for a hamburger chain attacking the poor quality of rival chains. (1984) The phrase was almost immediately transferred to other kinds of substance, especially in politics.