We report the first measurements of growth oscillations in high vacuum metalorganic vapor phase epitaxy (MOVPE). The reflection difference response of the surface is used for real‐time monitoring of the layer‐by‐layer growth of GaAs from triethylgallium (TEG) and arsine. The frequency of the optically detected growth oscillations is found to be proportional to the flux of TEG and to the growth rate. We expect our results to extend the more limited ranges of applicability offered by reflection high‐energy electron diffraction to allow the study of growth oscillations also in other MOVPE‐related growth techniques.