The removal of mid-spatial-frequency errors is a challenging issue in most subaperture polishing technologies. A novel "grolishing" technology has been developed to deal with grinding errors of spatial wavelengths from 1 to 50 mm with the help of power spectral density analysis and filter theory. This grolishing process was implemented on Zeeko's IRP polishing machine, on which all the subsequent polishing was performed. This has greatly reduced the process time. Although different abrasive have been used, the process is self-contained. The process parameters have been optimized to leave an edge upstand of peak-to-valley of 1 μm over a width of 40 mm.