Composite electrodes of yttria-stabilized zirconia (YSZ) with La0.8Sr0.2MnO3 (LSM), La0.8Sr0.2FeO3 (LSF), and La0.8Sr0.2CoO3 (LSCo) were prepared and tested as solid oxide electrolyzer (SOE) anodes and solid oxide fuel cell (SOFC) cathodes at 973 K, using cells with a YSZ electrolyte and a Co-ceria-YSZ counter electrode. The LSM-YSZ electrode was activated by cathodic polarization but the enhanced performance was found to be unstable during electrolysis, with the electrode impedance increasing to near its unenhanced state after 24 h. LSF-YSZ and LSCo-YSZ electrodes exhibited a nearly constant impedance, independent of current density, during both SOE and SOFC operation. The performance of an LSF-YSZ composite for electrolysis current densities above 200 mA/cm2 was unaffected by changing the O2 partial pressure from ~10–2 to 1 atm, while the lower O2 pressure harmed the performance of the LSCo-YSZ composite. The implications of these results for the characterization and optimization of SOE anodes is discussed.