The reduction and subsequent reoxidation of isolated vanadate species supported on silica was investigated using temperature-programmed reduction and oxidation, along with in-situ XANES and Raman spectroscopy. Approximately 70-80% of the vanadium was reduced to V3+ after reduction in H-2 at temperatures up to 923 K. Upon reduction, the vanadyl oxygen was removed and the three remaining V-O bonds are lengthened by 0.2 angstrom. The vanadate species are rapidly reoxidized when exposed to O-2, with the amount of oxygen uptake matching well with the amount removed during reduction. In-situ Raman spectroscopy during reoxidation in O-18(2) showed that significant scrambling occurs between gas phase oxygen and surface oxygen species during the reoxidation of the vanadate species.