Based on the empirical pseudo-potential within the virtual crystal approximation including the effective disorder potential, calculations of the electronic structure of the zinc blende quaternary GaxIn1-xAsyP1-y alloys have been studied. The direct and indirect energy gaps of the considered alloys have been determined over the entire composition x and y in condition of being lattice matched to GaAs substrate. In addition, the effect of temperature and hydrostatic pressure of these energy gaps have been studied. Comparison of the calculated results with the experimental and published data showed good agreement (C) 2013 Elsevier B.V. All rights reserved.