We carried an ab initio investigation on the properties of carbon incorporation in silicon oxide, which leads to stable crystalline phases of silicon oxycarbide. We showed that silicon oxide remains energetically and structurally stable with carbon incorporation. The resulting material has a reasonably large bulk modulus and a large band gap. The electronic band structure of silicon oxycarbide (SiCO) resembles that of silicon oxide, except with the introduction of deep levels, with carbon character, in the valence band. Additionally, its band gap is larger than that of silicon oxide.