Morphological and molecular data indicate that two valid species exist in Europe within the two species complex, Onthophagus vacca and O. medius. The aim of our study is to check specimens from major museum collections and some personal collections from the country and to assign them to O. medius or O. vacca. We have examined 417 specimens belonging to the following collections: “Grigore Antipa’’ National Museum of Natural History Bucharest, Brukenthal National Museum-Natural History Museum, Department from Sibiu and the authors’ personal collections. We extracted elevation data for each specimen and we created distribution maps. The biogeographic distribution for Romania shows the ranges of O. vacca and O. medius overlap and they are found in all the country’s bioregions. Our study shows a high ecological plasticity in both species. Our data apparently indicate a preference for altitudes below 500 meters, possibly influenced by non-random sampling.