We report the fabrication and characterization of large area (1 × 1 cm2) Ga0.84In0.16As0.68P0.32 (Eg = 1.50eV) and Ga0.51In0.49P (Eg = 1.88 eV) solar cells. The cell structures were grown by gas-source MBE on 2"(100) GaAs substrates. For the GaInAsP material, both n-on-p and p-on-n structures having wide-gap Ga0.51In0.49P window were studied. The GaInAsP n-on-p cells showed significantly better active area conversion efficiencies (17.8% at AM0, 1-sun illumination) than p-on-n structures (13.0%, same conditions) mostly due to lower sheet resistance of the n-type GaInAsP emitter layers. For GaInP cells the best conversion efficiency of 11.0% was achieved for windowless shallow homojunction n-on-p structure. Since only single layer of SiNx was utilized as an antireflection coating for all the cells, we believe that the application of an optimized two-layer antireflection coatings could increase the efficiencies up to 19% and 14% for GaInAsP and GaInP solar cells, correspondingly. The excellent uniformity in all the cell parameters across the 2" wafers indicates that larger area solar cells (up to 10 cm2) can be fabricated.