Zincblende semiconductor materials such as GaAs and ZnSe are very promising for the generation of tunable IR signals by quasi phase-matched nonlinear optical frequency conversion. Orientation patterned GaAs crystals (OP-GaAs) were grown by low-pressure hydride vapor phase epitaxy (HVPE) on lithographically prepared templates.. Cathodoluminescence (CL) imaging was used to study these epitaxial films, which consist of periodic domains of inverted crystallographic orientation. The challenge is to achieve thick, vertical domains and to minimize sources of optical loss. Both the domain walls and crystal defects may contribute to transmission losses, therefore, a characterization of both is necessary to improve the OP-GaAs crystal performance. The stress and non radiative recombination activity of the domain walls were investigated. The presence of dislocation glide was revealed and CL spectral imaging was used to observe the stress distribution around both the domain walls and the dislocations.