The incident took place off Curlew Road in Lees on Monday 24 January.
It's understood the attack took place between 6.30pm and 6.45pm in a place known locally as The Valley.
The offender is described as being white, approximately 5ft 8in tall and of a skinny build. At the time of the incident, he was wearing a grey tracksuit with a black mask and cap.
PC Hussain, of GMP's Oldham district, said: "This news will, undoubtedly, worry local residents but we are carrying out extensive enquiries to find the person responsible for this crime.
"I'd ask anyone with information - particularly dash cam footage from the roads surrounding The Valley - to contact us or Crimestoppers as soon as possible to assist us with our investigation."
Anyone with information should contact police via 0161 856 9094 or the GMP website quoting 2464 24/01/22. Alternatively, the independent charity - Crimestoppers, anonymously, on 0800 555 111.
