In this article we present the bandgap engineering and spectral properties of ZnO-CdS and ZnO-TiO2 nanocomposites prepared by colloidal chemical synthesis. The optical bandgap (Eg) of the material is tunable between 2.62 and 4.12 eV. Emission peaks of ZnO-CdS change from 385 to 520 nm and those of ZnO-TiO2 change from 340 to 385 nm almost in proportion to the changes in Eg. It is possible to obtain a desired luminescence color from UV to green by simply adjusting the composition. ZnO-CdS and ZnO-TiO2 are potential nanocomposite materials for the tunable light emission.