Size dependent variations in resistive switching using a metal-semiconducting oxide model to examine the underlying mechanisms are reported. In the range of 20 nm to 200 nm, Au nanoparticle/SrTiO3 interface transport properties are size dependent. The size dependence is attributed to the combination of geometric scaling and size-dependent Schottky properties. After electroforming, the observed “eight-wise” bipolar resistive hysteresis loop is modulated by trap/detrap process. The size-dependent high resistance state is consistent with changes in both the interfacial area and Schottky properties. The low resistance state exhibits size independent resistance through the dominant fast conductive path. Detrapping requires more work for smaller interfaces due to the associated larger built-in electric field.