A teenager suffered a broken jaw when he was attacked in Chipping Norton on Saturday.
The incident happened at about 1am near the town hall.
The 17-year-old youth, from Wakefield, in West Yorkshire, was taken to the John Radcliffe Hospital, in Oxford, with facial injuries, including a broken jaw, after being assaulted.
He was released from hospital on Sunday.
Dc Grahame Lea said: "This young man was part of a group from Yorkshire visiting Chipping Norton.
"He had been at the receiving end of a serious assault and we need to speak to anyone who was in the area at the time and saw this fight or whatever may have led up to it."
Anyone with information should call Dc Lea on 08458 505505 or Crimestoppers on 0800 555111.
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