A 27-year-old man needed 17 stitches after being assaulted at the Blue Boar pub.
He was attacked between 11pm and midnight on Friday, June 20 in the rear garden and then at the front of the Newbury Street pub.
The victim sustained a deep cut to the forehead, requiring nine stitches, and a cut to the jaw, which needed eight stitches.
Thames Valley Police - which only released information yesterday - said the suspect was white with a red shirt, dark red jeans and grey plimsolls.
A 38-year-old Wantage man was arrested on suspicion of grievous bodily harm and bailed to July 25.
Anyone with information should call Det Con Francesca Griffin on 101 or Crimestoppers anonymously on 0800 555 111.