Single-domain crystals of MTiOAsO4, where M equals K, Rb, & Cs were grown from various alkali arsenate self fluxes. Their refractive indices and Sellmeier coefficients were determined with critical angle of total reflection measurements. Type-II phase-matched SHG was used to check for crystal domains and to determine the accuracy of the Sellmeier coefficients. The dij coefficients for second harmonic generation were determined with Maker-fringe technique at 1.06 micrometers . Electro-optic coefficients rji were determined with interferometry. This paper reports the above measurement results and discusses the systematics of crystal structure, birefringence, and optical nonlinearities among the pure isomorphs and their solid-solutions. Calculated SHG cut-offs and tuning curves are also reported.