This study investigates the effects of annealing atmosphere (air vs. oxygen) and temperature on the properties of RF-sputtered VO2 thin films. XRD analysis revealed that annealing in an oxygen atmosphere preferentially enhances the formation of the monoclinic VO2 phase over V2O5 and reduces the crystallization temperature to 300 °C. A strong correlation was observed between increasing annealing temperature, surface roughness (AFM), and oxygen content (SEM-EDX), a trend that was more pronounced and linear under an oxygen atmosphere. The results demonstrate that oxygen annealing is a superior processing route, optimizing phase purity, morphological stability, and stoichiometry for enhanced metal-insulator transition properties.