The present work addresses the microstructural design of Galfenol and Alfenol, which are magnetostrictive materials used in bending mode energy harvesters. Galfenol and Alfenol have been attracting much interest during the last few decades as they provide bi-directional coupling between mechanical and magnetic properties. This magneto-mechanical coupling generates electrical energy in distinctive energy harvesting mechanisms that use mechanical or magnetic input. One favorable approach would be enhancing the energy efficiency by optimizing the material properties through the control and design of the underlying microstructure. However, to the best of our knowledge, there is no effort for designing Galfenol and Alfenol microstructures to maximize energy efficiency. Therefore, we present a computational design study to find the optimum Galfenol and Alfenol microstructures that can maximize the energy efficiency for bending mode energy harvesters. We model the effects of the crystallographic texture on the mechanical and magnetic properties and develop a computational model to represent the magneto-mechanical coupling. The outcomes of our computational strategy revealed that the optimum design solutions are highly textured polycrystals. Moreover, the optimum Galfenol and Alfenol microstructures are found to provide around 80% and 32% energy efficiency, which are higher than the known optimum efficiency level for the same materials.