Due to the growing need from the aviation and maritime industries for biomimetic technology during the past 20 years, many researchers have concentrated on simulating such complex bio-systems. One fascinating phenomenon in the field of animal propulsion and mobility is the wing-flapping action. In the numerical simulation, either moving or deformable meshes are used to numerically handle the moving bodies. One of the moving mesh techniques that can accommodate a flapping foil motion is overset (or chimera) [1]. The overset is a technique that has been passed through multiple stages of development in OpenFOAM, the free open-source CFD tool. However, the capability of simulating a deformable moving body, such as a flexible flapping foil, has not been solved in OpenFOAM. In this work, a specific library has been developed to improve the OpenFOAM overset module in handling such complex motion and deformation problems. The developed library has been verified using the physical model defined by [2], consisting of heaving and pitching NACA0012 foil whose flap and slat morph during the flapping cycle. In this work, the foil is first meshed as an overset zone and made to heave and pitch in uniform flow. Figure (1.a) presents an image of the current foil arrangement to help understand the flexibility of flapping foil. The result of our work is illustrated in figure (1.b) where we managed to combine the deformation of the foil with the flapping motion in the front mesh while keeping the background mesh unmoved.