Dense thin films of the solid oxide fuel cell cathode material La0.6Sr0.4CoO3-δ were studied by operando X-ray absorption spectroscopy under sinusoidal voltage perturbations. This approach showed good agreement with previous steady-state µ-XAS measurements, but with high effective p(O2) resolution over several orders of magnitude. Co oxidation state varied strongest under a 0.5 Hz perturbation suggesting, in agreement with linear impedance, that oxygen exchange kinetics are most active at this timescale. Furthermore, the local structure around Co atoms response varied at different timescales; however, interpretation was limited with only preliminary analysis. Altogether, this approach was shown as a successful step towards developing a technique sensitive to local chemical state that can also separate processes by timescale.