Two men distracted owner Vijay Patel from Wallingford by chatting to him in a friendly manner as a third took a crowbar to the back room door.
Vijay said the theft had been well planned. "It was all so fast. I didn't hear anything; it was only when I came down to sort something out at the back that I realised the door was open."
The store has a CCTV system, but it was not angled to cover the stock room area.
Police are appealing for witnesses, as the store was full of customers at the time the incident took place.