Sustainable electrocatalysis of the oxygen evolution reaction (OER) constitutes a major challenge for the realization of green fuels. To avoid using critical raw materials multimetallic oxides based on Ni and Fe have been proposed in alkaline media. However, oxide phases evolve under OER conditions resulting in ill‐defined oxyhydroxide structures precluding the identification of descriptors to improve performance. Here, we have studied Fe‐Ni‐Zn spinel oxides, with a well‐defined crystal structure, as a platform to obtain general understanding on the key contributions. The OER reaches maximum performance when: (i) Zn takes place in the Spinel structure, (ii) very dense, equimolar 1:1:1 stoichiometry sites appear on the surface as they allow the formation of oxygen vacancies where Zn favors pushing the electronic density that is pulled by the octahedral Fe and tetrahedral Ni redox pair lowering the overpotential. Our work proves cooperative electronic effects surface active sites as key to design optimum OER electrocatalysts.