We have previously reported on electrically pumped random lasing (RL) with onset voltages at least 3.3 V from ZnO-based light-emitting devices with metal-insulator-semiconductor (MIS) structures in the form of Au/SiO2/ZnO. Here, by inserting an ∼5 nm thick MoO3 layer between SiO2 and ZnO films in the aforementioned MIS structured device, the RL onset voltage is decreased to only ∼2.6 V and, moreover, the output optical power is multiplied several times. Such improved RL performance is ascribed to the enhanced injection of holes into ZnO via the MoO3 interlayer that features a low-lying conductive band and therefore a large work function.