Police are investigating.
The 73-year-old victim walked past a group of young people at around 2am on Saturday who accused him of hitting his dog, which he denied.
Four males then surrounded him and kicked and punched him repeatedly.
The victim was left with two black eyes, bruising on his face, arms and legs and a pulled muscle in the back.
One of the offenders is described as a mixed race male and around 18-19 years old with Afro style hair, which was brushed up.
The second offender is described as a white male, aged 18-19 years old with straight, blonde shoulder length hair.
Investigating officer PC Mark Russell of the Incident & Crime Response Team at Didcot police station said: “Thames Valley Police takes reports of assault very seriously.
“Whatever the time of day, members of the public should feel safe walking around their local communities.
“We are appealing to anyone who might have seen or heard the incident to contact us.
“We are also asking anyone with information on the offenders to get in touch and for anyone with home CCTV, to check their recordings for any footage that could help this investigation.
“Please call us on 101 quoting reference number 43210341488 or make a report online if you can help.
“Alternatively, you can call independent charity Crimestoppers on 0800 555 111 for 100% anonymity.”