In this paper, oxygen evolution reaction (OER) mechanism in La0.6Sr0.4Co0.8Fe0.2O3 was investigated in KOH solution by electrochemical impedance spectroscopy (EIS) and voltammetric measurements. The Tafel slopes and reaction orders evaluated in this paper are consistent with the B. O'Grady's Path for oxygen evolution on oxides. The activation energy for OER in La0.6Sr0.4Co0.8Fe0.2O3 was 28.3 kJ mol(-1). The obtained apparent porosity of La0.6Sr0.4Co0.8Fe0.2O3 electrode is 48% and the roughness factor is around 1.6 x 10(4). The polarization resistance of La0.6Sr0.4Co0.8Fe0.2O3 is much low compared with other similar oxides. This can be due the high roughness and high porosity in addition to the low active energy for the process. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.