Bicester Village has closed as a consequence and five fire engines are on the scene battling the blaze.
One eyewitness told the BBC: "Carluccio's restaurant is on fire, flames are coming out of the roof. It's chaos, with people running in all directions."
The fire service confirmed it was called at 08:40 GMT. Bicester Village said it was closed.
A large fire has broken out at a major shopping outlet in Oxfordshire.