We have studied the lateral epitaxial overgrowth by MOCVD of a variety of highly mismatched III-V semiconductors on GaAs substrates. For [001] substrates we determined the oxide stripe orientation that gives the maximum lateral growth rate to be ∼ 25^o from [110]. We successfully achieved that lateral overgrowth of In_xGa_1-xAs alloys on GaAs and found that the use of Bi as a surfactant led to an improvement in the morphology and luminescence uniformity. The studies have been extended to the lateral epitaxial overgrowth of InAs, GaP, and InP.