The simultaneous anodic oxidation of Pb2+ and CO2+ in a sulphamate bath containing suspended Co3O4 (or NiCo2O4) particles has been studied as a method for preparing composite oxides in which the particles are dispersed in a matrix consisting of PbO2 and hydrous Co oxides, CoOx with x < 2. The (PbO2 + CoOx) + Co3O4 composites thus prepared are very rough and their Co concentration, expressed as X-Co = N-Co/(N-Co + N-Pb), where N represents the number of atoms, approaches 0.5. As a result, they are more active catalysts in the oxygen evolution reaction than either PbO2 + CoOx or PbO2 + Co3O4 prepared in the past by our group. For samples prepared in the presence of particles, the potential required to evolve oxygen at a fixed current density varies roughly linearly with X-Co, irrespective of the fact that Co is present as Co3O4 or CoOx.