The extraction of energy from wind or water streams is generally accomplished by means of rotary systems. However, it is recognized and it has been demonstrated that oscillating wings can also be used for this purpose. A newly developed oscillating-wing wind and hydropower generator is described. Its potential for the generation of electric power from tidal flows and high-altitude jet streams is studied using two-dimensional Navier-Stokes simulations at Re = 20,000. Results for a single NACA0014 wing power generator undergoing nonsinusoidal pitch-plunge motion indicate around 17% increase in power generated and around 15% increase in efficiency over that for sinusoidal motion. Two airfoils operating in tandem, undergoing both sinusoidal and nonsinusoidal motions, are also studied. It is found that for sinusoidal motion both averaged power output and efficiency per foil are reduced by around 20% for tandem configurations compared with a single foil in sinusoidal motion, and similar performance reductions are experienced for nonsinusoidal motions.