A simulated amorphization and recrystallization technique has been used to explore how a polycrystalline metal-oxide thin film can be synthesized selectively on an MgO(100) substrate. The simulations indicate that by introducing a polycrystalline SrO "buffer-layer", sandwiched between the support and overlying thin film, polycrystalline thin films of CaO and BaO can be fabricated. Conversely, our findings suggest that without the buffer layer, neither the CaO nor the BaO exhibit polycrystallinity when supported on an MgO(100) substrate, This suggests that the polycrystalline buffer layer acts as a template in directing the structure of the overlying metal oxide resulting in polycrystalline thin films.