The redox-controlled driven oscillatory template exchange between phosphate (P) and vanadate (V) anions enclosed in an {X2M18} cluster is reported. Extensive investigations using a range of techniques, including correlated ESI-MS, EPR, and UV-vis as a function of reaction time, showed that six complete oscillations interconverting the capsule species present in solution from {P2M18} to {V2M18} were possible, provided that a sufficient concentration of the TEA reducing agent was present in solution.