A new class of commercial platesetters, called computer-to-plate (CtP) systems, has been introduced in the graphic arts industry in the past few years. As opposed to conventional systems that use an analog mask, these CtP systems employ direct digital imaging methods to generate patterns on metal plates used for offset printing. By eliminating this intermediate mask step, CtP platesetters enable users to transfer images directly from the computer to the plate, thus reducing cost and cycle time. The Grating Light Valve (GLV) is a diffractive MOEMS device that has been successfully implemented as the spatial light modulator in a commercial CtP platesetter for the graphic arts industry. The combination of high power handling capability, fast modulation rate, and large number of pixels on the GLV allows for increased printing speed. Properties of the GLV, such as analog gray scale, and pulse width modulation can be used to increase print quality. In order to create images on the plates, infrared laser illumination is focused onto the GLV device, which reflects the beam with controlled intensity onto a photo-thermal medium. While offering advantages in quality and throughput, the high pixel count and form of the GLV presents some challenges in illumination and projection onto the printing plate. This paper will describe the system architecture and method of operation for a GLV-based optical write engine, and show performance and results.