Rocksalt-structured (RS) Mg
x
Zn1-x
O films with x=0.65-1.0 were grown on MgO (100) substrate by the mist chemical vapor deposition method. Comparative study for the RS-Mg0.92Zn0.08O films grown under slow and rapid-cooling rates apparently showed simultaneous reductions in the surface pit density, full width at half maximum values for the X-ray diffraction peak, and defect-related cathodoluminescence (CL) for the film grown under the slow-cooling rate. CL spectra for the RS-Mg
x
Zn1-x
O films grown under the slow-cooling rate eventually showed near-band-edge emission peaks in 180-190 nm spectral range for MgO molar fraction x≥0.92 at room temperature.