The electronic and optical properties of the MgxZn1-xS semiconductor ternary alloys crystallizing in the Zinc Blende structure are calculated using the empirical pseudopotential method (EPM) coupled with the virtual crystal approximation (VCA). The composition dependence of the direct and indirect band gap energies as well as the antisymmetric gap are investigated in the composition range 0 up to 1. Other quantities such as refractive index and coefficient of reflection are also obtained by means of different existing models. Our results are generally in good agreement with those available in the literature. The obtained informations could be useful for the feature design of blue wavelength optoelectronic devices.