Doped M:ZnO nanoparticles (Zn/M = 50:1 or 20:1; M = AgI, CoII, CuII, EuIII, MgII, MnII) have been produced by an easy, reproducible, and fast inverse miniemulsion approach, enabling the co-precipitation of the nanocrystalline oxide in a confined space. Unexpectedly, the formation of crystalline materials took place at room temperature. Suspensions were characterized by dynamic light scattering and UV/Vis spectroscopy, whereas precipitated powders were characterized by X-ray photoelectron spectroscopy, X-ray diffraction, transmission electron microscopy, inductively coupled plasma atomic emission spectrometry, and thermogravimetric analysis. The particles obtained showed preferential growth along the [0002] direction with a size of 70 nm, whereas along the other directions average sizes of between 26 and 33 nm were determined. The analyses confirmed successful doping in all cases but one: In fact, the Ag-doped sample is a nanocomposite consisting of metallic silver clusters dispersed in the ZnO matrix. Red emission from the ZnO:Eu sample was evidenced upon excitation at around 465 nm.