An electrical fire broke out in the roof of Waitrose at Pear Tree service station.
The fire at the Welcome Break services started at about 2.15pm on Saturday.
Fire crews from Rewley Road, Kidlington and Slade Park all helped to battle the blaze for an hour.
A spokeswoman for the fire service said that the shop was evacuated while firefighters were tackling the blaze.
She added that no one was hurt in the incident.
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