The victim was attacked in Gillians Park in Blackbird Leys at 20:48 BST on Wednesday and remains in hospital with serious injuries to his arms.
One suspect is described by police as a black man, aged about 24, of large build, with short hair.
Another is thought to be about 25 years old, with a ponytail and beard.
Det Sgt Wojciech Spyt said: "We would like to appeal to any witnesses in the area at the time of the incident who may have seen a group of four men running down Dunnocks Way towards Greater Leyes."

A crane was used to lift the scanner into place and the operation took several hours to complete.
The multi-million pound investment has been partly funded by charitable donations.
By 2012, the scanner appeal had raised £2m, and back then the Belfast Health and Social Care Trust said it expected the machine would be in place by 2013/2014.
At that stage, the total capital cost was estimated at £4m, with additional annual running costs of £1.9m.
The then Health Minister Edwin Poots committed £2.75m towards the project in November 2012 and described it as a "vital service".
He said he was delighted that it was finally going to be installed and that the delays had been caused by practical issues.
"Obviously it is something that the Belfast Trust were dealing with but the hospital that it is being placed in is a very old building," he said.
"The first problem that they came across was asbestos and there was considerable asbestos removal to take place, so that was the first delaying factor.
"Another thing that impacted on it was that the actual scanner is a considerable weight and the ground had to be piled for the scanner to be installed.
"That piling was taking place actually within a building, so one can understand that that was a huge engineering challenge to take on."
Mr Poots said that once it was installed it would have "life-saving consequences" and make a "huge difference" for the services provided at the children's hospital.
Brian Barry, the Belfast Health and Social Care Trust's director of specialist hospitals, said the new scanner would help to reduce waiting times.
"Previously our children in Northern Ireland had to go and have MRI scans in an adult environment," he said.
"We now have a whole new purpose-built, child-friendly environment and have increased the amount of sessions available, so there is more service and a better service, Monday to Friday."
The scanner should be operational within two months and will be used in the diagnosis of a wide range of medical conditions, including cancer.

George Hamilton was speaking to MPs on the Northern Ireland affairs committee.
It is investigating how a UK exit from the EU could affect Northern Ireland.
Mr Hamilton said the PSNI would "not take a position on exit or not" and would work with whatever circumstances are in place after the EU referendum.
Voters will go to the polls in June to decide whether the UK should remain a member of the EU.
Asked on whether an exit from the EU would affect policing, Mr Hamilton said: "I think all of this is probably doable with an exit, but it will be slower, complicated and more costly is the view we would take from a practical policing perspective."
But he said the PSNI had a "very good working relationship" with a number of police forces in non-EU countries, "most notably America".
Mr Hamilton, who appeared before the committee with Assistant Chief Constable Will Kerr, also said he did not think the PSNI's link with the Irish police would suffer in the case of an exit from the EU.
He said "the relationships are secure".
He added that if a so-called Brexit - a shorthand term for a UK exit from the EU - took place he was "absolutely sure the quality of the relationship and the professionalism of both organisations would not be diminished".
The committee is examining areas like the economy and the border with the Republic of Ireland.
It has already heard evidence from a wide range of politicians and business leaders.

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27 January 2015 Last updated at 07:56 GMT
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