Perovskites are a family of complex oxides with the nominal formula AMO₃, where A is lathanide or alkali earth and M is typically a transition metal. They are of great interest as replacements for precious metals and oxides used in the oxygen evolution reaction (OER). Perovskite electrocatalysts have been shown to have greater specific activities than precious metals and their oxides, but high mass activities have not yet been realized due to the complex nature of perovskite oxide surfaces and inadequate synthesis techniques which often result in unwanted phase impurities and micron-scale materials. In this presentation we demonstrate the precise control over the chemical composition and structure of a series of perovskite and Ruddlesden-Popper electrocatalysts that are highly active for OER. The reaction pathways are perturbed by the direct modification of the perovskite structure by selective cation replacement and by promotion of catalyst-carbon support-interactions. Specifically the synthesis and electrochemical evaluation of a series of Ruddlesden-Popper (RP) La_0.5Sr_1.5Ni_1-xFe_xO_4+δ  will be reported that describe the highest catalytic activities reported for RP/perovskite matierials to date. These results will be described in the context of benchmarking to IrO₂ and Pd and definition of the structure, electronic configuration and catalytic pathways. Electroanalytical techniques such as rotating disk electrochemistry and cyclic voltammetry are used in conjunction with materials characterization enabled by dynamic light scattering, electron microscopy, nitrogen sorption, X-ray photoelectron spectroscopy and X-ray diffraction. It will be demonstrated that these highly active perovskite catalysts are an emerging replacement for the precious metal catalysts.