In this manuscript, we have studied the structural, electrical and thermoelectric properties of bulk ZnSnO by post growth annealing method. X-Ray Diffraction data showed that the crystallinity was found to be improved y annealing up to 700oC due to compensation of oxygen vacancy type donor defects. But further annealing forced the oxygen atoms to diffuse into the interstitial sites, therefore causes degradation in the crystal quality. Thermoelectric properties were increased with annealing temperature up to 700oC and then decreased due to further annealing. The sharp enhancement of thermoelectric properties is due to mobility increase of carriers.