Newlyweds Beyonce Knowles and Jay-Z shunned the posh food at New York's Costume Institute Gala on Monday night- instead heading off to a local burger joint after the event.

The stars - who wed in a secret ceremony last month- walked the red carpet at the city's Metropolitan Museum and attended the glitzy fashion party.

After they left, they decided to pick up dinner on their way home, stopping at a fast food restaurant to buy cheeseburgers and fries.

And, even though the restaurant was closed, staff opened their doors after-hours to serve the couple.

A source tells New York Post gossip column PageSix, "Pop Burger had just closed. There was a loud knock on the door, and Jay and Bey, who was still in her ball gown, were at the door with their Maybach (car) waiting."