Oxygen exchange on thin films of La1-xSrxCoO 3-δ (LSC) was studied at high temperature using linear and nonlinear electrochemical impedance spectroscopy (EIS and NLEIS). Both the chemical capacitance and nonlinear kinetics suggest that the thermodynamic characteristics of the films are shifted from that of freestanding bulk LSC of the same cation composition. For La0.6Sr0.4CoO 3-δ (LSC-64), the film thermodynamics appears to vary with fabrication technique and conditions. For La0.8Sr 0.2CoO3-δ (LSC-82), our preliminary results suggest that thermodynamics governing the surface and bulk differ, possibly due to segregation of cations at the electrode surface. All results appear to be explainable under the assumption that oxygen reduction at the surface is limited by dissociative adsorption.