Forty tonnes of straw was destroyed in a fire at Tor Farm, Allington, near Chippenham.
The fire broke out at 9.12pm last Wednesday.
Two fire crews from Chippenham and a water carrier from Royal Wootton Bassett attended but, due to the scale of the fire, two more crews from Corsham attended.
About 25 fire fighters were involved and once the fire was surrounded and protective jets were in place the operation was scaled down at 1am.
Crews allowed the fire to burn itself out under control.
Farmer Brian Tayler and his daughter, Megan Wood, helped the fire fighters by moving 30 beef cows and calves from an adjacent shed to another area. They were unharmed.
Engineers from Southern Electric also attended and isolated the power to an electricity pole which was near to the barn where the fire was.
An investigation by Wiltshire Fire and Rescue Service has not determined what caused the fire.