This dataset contains high-throughput density functional theory (DFT) computations on ternary and quaternary alloys of II-VI zincblende semiconductors with Cd or Zn at the cation site and S, Se or Te at the anion site. Computed properties include formation and mixing energies, electronic band gaps, and optical absorption spectra, from different levels of theory (GGA-PBE, HSE06, with and without spin-orbit coupling).