The barn fire at Abbey Farm, North Weston, near Thame has now been put out.
Fire crews are still on the site but say the blaze, which began on Monday night, has been extinguished.
It involved 20 tonnes of manure along with hay and farm machinery.
Station Manager Marcus Reay said: "This was called in by an off-duty firefighter from Slade Fire Station in Oxford. The owners of the building were very quick in removing a mechanical digger from the barn, evacuating horses and leading them to safety from the nearby stables."
He said the fire service had been busy over the past week with countryside fires because of the warm, dry weather and added: "The sunny weather over the past few weeks has made the grass and edges of fields very dry so I would ask the public and those who work on farms or in the countryside to take extra care."