Research on the classic binary semiconducting oxides TiO₂, WO₃, and Fe₂O₃, has revealed many attractive properties of these materials for application as photoelectrodes in direct solar-to-fuel conversion devices. However, no binary oxide has yet been found with ideal properties for efficient and robust application in a photoelectrochemical device. Ternary and multinary metal oxides represent an appealing opportunity to develop materials with tuned optoelectronic properties perfect for solar-to-fuel application. Herein, some of the latest advances with employing complex metal oxide semiconductors in photoelectrochemical devices are described. The importance of electronic band composition is mentioned along with describing recent research progress with select vanadates, niobates, ferrites, cuprates and bismuthates. Strategies to engineer the performance using doping, nanostructuring, and heterojunction formation are highlighted. The influence of carrier diffusion length, band gap energy, band edge positions, and absorption coefficient are mentioned in the context of the limitations of each material. Finally, an outlook on the development of multinary oxides for future application is presented in view of the current state-of-the-art.