Crews were called to Carding Mill Valley, Church Stretton, this morning after the heater caught fire in the National Trust chalet pavilion.
Two fire engines were sent, but staff managed to put the fire out with an extinguisher before fire service personnel arrived.
A fire service spokesman said: "At 9.06am we received a call reporting a fire classified as property fire in the National Trust chalet pavilion at Carding Mill Valley.
"Two fire appliances were mobilised from Church Stretton and Craven Arms.
"Fire involving oil filled electric heater in first floor office.
"Fire extinguished by staff using extinguisher prior to arrival of fire service.
"Fire crew cut away carpet and furniture to check for hot spots."
The stop message was received at 9.24am.