Beyonce Knowles and Jay-Z shunned the posh food at New York's Costume Institute Gala on Monday night and decided to head off to a local burger bar instead.

The stars, who got married 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 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."