A metal pole and a sheet of metal were used in the attack.
The incident happened behind the City Arms Pub on Cowley Road at 4.30am on Friday 17th July.
The victims, a man in his forties and a man and woman in their twenties were assaulted with a wooden pole and a sheet of metal.
The man in his forties needed hospital treatment for a head injury but has since been discharged. The other two victims suffered cuts and bruising.
Investigating officer PC Katherine Miles, based at Cowley police station, said: “I am releasing these CCTV images as I believe that these men could have information that could help my investigation.
“This was an unprovoked attack and I am appealing to anyone who saw or heard anything to come forward.
“If you recognise these men, or think that one of them might be you, please get in touch.
“You can contact us using our online reporting form, quoting reference number 43200218734, or by calling the non-emergency number 101.
“Alternatively, you can call Crimestoppers 100% anonymously on 0800 555 111.”