Bandgap engineering is central to the design of heterojunction devices. For heterojunctions involving monolayer-thick materials like MoS2, the carrier concentration of the atomically thin film can vary significantly depending on the amount of charge transfer between MoS2 and the substrate. This makes substrates with a range of charge neutrality levels - as is the case for complex oxide substrates - a powerful addition to electrostatic gating or chemical doping to control the doping of overlying MoS2 layers. We demonstrate this approach by growing monolayer MoS2 on perovskite (SrTiO3 and LaAlO3), spinel (MgAl2O4), and SiO2 substrates with multi-inch uniformity. The as-grown MoS2 films on these substrates exhibit a controlled, reproducible, and uniform carrier concentration ranging from (1-4) ×1013 cm-2, depending on the oxide substrate employed. The observed carrier concentrations are further confirmed by our density-functional theory calculations based on ab initio mismatched interface theory (MINT). This approach is relevant to large-scale heterostructures involving monolayer-thick materials in which it is desired to precisely control carrier concentrations for applications. © 2021 Author(s).