VO2 thin films were produced on sapphire and silicon substrates through post-deposition ex-situ thermal treatment of V2O3 and VOx films. Thin epitaxial films of V2O3 on sapphire and amorphous VOx films on silicon substrates were grown using oxygen assisted molecular beam epitaxy. The post-deposition annealing was performed at different temperatures using an Ar flow. Structural, optical and electrical characterizations were performed to confirm the transformation of the films. The transformed films present a change in resistance across the metal to insulator transition of four orders of magnitude for annealed V2O3 on sapphire and around one order of magnitude in the case of annealed VOx on silicon.