Tankers on route to the fire in Lemongum road to could see black smoke issuing from the fire.
The shed, which housed 4 bays of hay and some small machinery, was almost completely consumed by fire when they arrived.
Firefighters in breathing apparatus fought the fire for around 45 minutes before it was brought under control.
A dozer was used to pull apart the remaining hay bales to help extinguish them.
7 tankers from Yellingbo, Hillcrest, Cockatoo, Gruyere, Hoddles Creek, Seville and Wandin attended the fire, in addition to Bayswater BA unit and Gruyere Big Fill.
A fire investigator has visited the scene. Early indications are the fire may have resulted from a ride on mower.