Her visit is believed to be the first time a sitting monarch has attended a Cabinet meeting in at least 100 years.
Cabinet members presented her with a gift of 60 placemats in honor of her Diamond Jubilee.
The government said the queen attended Tuesday's meeting as an observer - not as a contributor - in honor of her 60 years on the throne. But her visit has raised some eyebrows for appearing to blur the traditional line between government and monarchy.
As head of state, the queen performs some ceremonial and formal duties related to government but must remain neutral on political matters.