Solid Oxide Fuel Cell (SOFC) cathodes in use today generally use perovskite oxides to efficiently catalyze the oxygen reduction reaction, O2(gas) +2e- → 2O2- (solid). For many of the most active materials this process is strongly correlated to the surface exchange coefficient, k*, which measures how easily oxygen enters and leaves the material. In this talk we discuss our work using atomistic simulations to model the steps in the oxygen reduction reaction on ABO3 perovskite surfaces. We focus on (001) surfaces of (La,Sr)CoO3 and (La,Sr)MnO3, two widely studied SOFC cathode materials. We primarily find that the step of O adatoms finding surface vacancies is rate limiting, and find large differences between AO and BO2 surfaces in (La,Sr)CoO3 but not (La,Sr)MnO3. These results provide a foundation for interpreting experiments and guiding materials design of highly active and stable cathodes.