Broader impactHigh quality ultra-thin oxide films such as zirconia are of tremendous importance in energy sciences and technologies. Controlling oxide stoichiometry and oxygen concentration in the near surface regions of ultra-thin oxide films has a significant bearing on the functional properties of the synthesized oxide film and is of great significance. In this work, we show that atomic scale control of oxygen concentration in the near surface region of complex ultra-thin oxide films is possibleviaexternally applied electric fields (∼107V/cm). Zirconia ultra-thin films grown in the presence of electric field (∼107V/cm) are shown to have significantly improved rates of oxygen incorporation compared to native oxide. Precise understanding of the microscopic processes involved in electric field assisted oxidation is provided by the atomistic models employing dynamic charge transfer between atoms. We find that lowering of activation energy barriers in the presence of electric fields is responsible for the dramatic density and stoichiometry improvements in ultra-thin oxide films. Our atomistic simulations demonstrate a pathway to athermally tune oxygen concentration in the near surface regions of complex oxides that is of great importance to contemporary problems ranging from catalysis to energy and electronic device technologies.