This paper considers an application of the decentralized adaptive output feedback scheme developed by Jain and Khorrami (1997) to maintain global robustness to parametric and dynamic uncertainties among interconnections in large-scale power systems and also rejection of any bounded unmeasurable disturbances entering the system. The proposed design utilizes only feedback from local rotor angle measurements. The scheme is applied to a two-axis (fourth-order) model of the generator with a second-order turbine-governor model and an IEEE type I excitation control (fifth order) for each subsystem. The design presented is also applicable to higher-order models of the generator and turbine-governor system.