A systematic investigation of the formation of large grained rings in polysilicon by Q-switched laser irradiation has been performed. Parameters varied in this study were polysilicon thickness, substrate temperature and underlying oxide thickness. Increasing ring widths were obtained for increasing substrate temperature, polysilicon film thickness and underlying oxide thickness. The width of these rings was found to be independent of incident laser power above a certain threshold value. Surface morphology and the occurrence of cracking and ablation in these films as a function of these parameters was also investigated.