After the sharp transition to aridity that followed the “Green Sahara” episode 5500 years ago, human settlements took refuge in Egyptian oases, which have to varying extents been “Green Oases” for centuries. In that period, synchronous with the beginning of historical times, the desert’s aridity is generally regarded as broadly comparable to the current period. Natural and anthropogenic deposits studied during 13 excavation campaigns in Bahariya Oasis (Egyptian Desert) suggest that a fairly clear transition from a relatively green environment to much more arid landscapes occurred in the first millennia BCE and CE. This article aims at establishing the chronology of human occupations and environmental change within this period, by combining archaeological and radiocarbon data, using Bayesian modeling. It reveals that the drying up of the environment experienced by desert farmers occurred at some point between the reigns of Antoninus Pius and Caracalla (2nd–3rd century CE). The accuracy of the produced chronological models made it possible to highlight synchronisms between the end of this “Green Oasis” phase and comparable aridification phenomena on regional and interregional scales. Similar degradation processes on remote sites inside the Roman Empire might be explained by globalized anthropogenic agencies overlapping with a broader climatic drying.