We describe the generation of terahertz radiation by optical rectification in an electro-optic crystal mosaic. The mosaic is constructed from four single crystals of the organic salt dimethyl amino 4-N-methylstilbazolium tosylate and is approximately 1 cm2 in area. We characterize both the optical rectification efficiency and the spatial and temporal profiles of the generated terahertz beam, and find that the mosaic performs as well as a single crystal.