A method of making a mirror substrate for an interior rearview mirror assembly for a vehicle includes providing a glass substrate having a generally planar front surface, a generally planar rear surface and a circumferential perimeter edge about a periphery of said glass substrate and extending between the front and rear surfaces. A grinding wheel is moved around the periphery of a front perimeter portion of the glass substrate while rotating the grinding wheel to establish a ground generally rounded surface about and around the glass substrate periphery. A polishing wheel is moved around the glass substrate periphery while rotating the polishing wheel to establish a polished generally rounded surface about and around the glass substrate periphery. The polished generally rounded surface provides a smooth transition between the generally planar front surface of the glass substrate and a rear portion of the circumferential perimeter edge of the glass substrate.