Wurtzite quasi-alloys of MgZnO with MgO/ZnO superlattices have been grown by molecular beam epitaxy on sapphire substrates on high-quality ZnO buffer layers. The equivalent band gap energy of the quasi-ternary MgZnO was successfully tuned from 3.3 to 4.65 eV by changing the thicknesses of the MgO and ZnO layers. The near-band-edge cathodoluminescence was obtained from the MgO/ZnO superlattice without noticeable deep-level emissions and the multiple quantum well structures with MgO/ZnO superlattice quasi-ternary alloys were definitely fabricated, being capable of emitting ultraviolet (UV) luminescence from the well layers. These results suggest the promising potential of their optical functions for deep UV light emission and/or detection applications. © 2005 Elsevier B.V. All rights reserved.