Composite electrodes based on mixed valence oxide nanoparticles (Ox) embedded in an electrically conductive polymer (ECP) were investigated toward the oxygen reduction reaction (ORR). ECP was polypyrrole (PPy), and Ox was the spinel mixed valence oxide Cu1.4Mn1.6O4, which is known to be an electrocatalyst of the ORR in neutral and alkaline media. The main findings were that in such a composite electrode (i) the spinel lattice and the electrocatalytic activity of the oxide remained remarkably stable in acidic media where normally this oxide would be electrochemically reduced, and (ii) PPy retained its electrical conductivity at cathodic potentials where it would be normally in its insulating reduced state. Those composite electrodes sustained the ORR for hours without signs of deterioration.