Reaction-rate oscillations in CO oxidation over heterogeneous platinum thin-film catalysts were studied at atmospheric pressure where spatial coupling is due to gas-phase diffusion of reactant concentration gradients. The catalyst was perturbed locally by the introduction of CO directly above the surface, while the resulting spatiotemporal behavior was monitored using infrared imaging. The transient response of the system was studied in both the steady-state and oscillatory regimes, and comparisons are made between the observed behavior and predictions from models for the oscillations. Using these perturbations, global behavior was initiated using a localized effect. Similarities and differences between the induced oscillations and those occurring naturally are discussed, as are tests to vary the phase of the oscillatory cycle.