The incident took place at 4.30pm on Tuesday, as the victim was walking along the footpath at Avebury, Great Hollands.
Three men approached the victim and one asked for a light. The victim was then punched in the stomach and pushed from behind causing him to fall. The victim was then hit across the head before the offenders removed his backpack and ran away.
Items stolen include a brown Nike backpack, cash, bank documents, pay slips and clothing.
The victim sustained minor grazes to both hands and a bruised head. He did not require hospital treatment.
All three offenders are around 20-years-old. The first offender is a white man, with short facial hair, of average build and approximately 5ft 6ins. He was wearing a ski-hat, a short grey winter coat and jeans.
The second offender is a white man, and is approximately 6ft. He was wearing a dark baseball cap.
The third offender is a white man and approximately 6ft. He was wearing a ski hat.
If you have any information please contact Det Con Luke Simms from Bracknell police station via the 24-hour Thames Valley Police Enquiry Centre on 101.
If you don't want to speak directly to the police you can contact the independent charity Crimestoppers anonymously on 0800 555 111 or online at crimestoppers-uk.org. No personal details are taken, information is not traced or recorded and you will not go to court.