A 15-year-old girl was pushed to the ground and kicked and punched by two teenage girls.
Police are appealing for witnesses to the assault in Pye Street, Faringdon, about 7.30pm last Wednesday.
Officers said the victim had minor injuries after she was kicked and punched, but was not taken to hospital.
Police believe the incident was seen by an older woman.
PC Richard Farnell, of Abingdon police station said: "I am particularly keen to speak to a woman who may have seen the assault take place.
"The woman was in her mid-fifties, about 5ft 7ins tall, with straight shoulder length hair which was blonde or grey in colour. She was wearing a grey coat. I would ask this woman and any other witnesses to contact me via the 24-hour Thames Valley Police enquiry number 101."
Both offenders are white and aged 15 to 16.
One was about 5ft 5ins tall, with long straight brown hair, and was wearing pink tracksuit bottoms, a white and yellow striped t-shirt with a black jacket over the top, a pink leopard print scarf and pink trainers.
The second girl was about 5ft 6ins tall, with straight blonde hair, and was wearing a blue top, purple trainers and black leggings.
Anyone with information should call police on 101, or Crimestoppers anonymously on 0800 555 111.