In this work olive samples of Gemlik variety originated from Turkish regions Serinyol, Bahce, Saricam, Tarsus and Mudanya were harvested at five different times during fruit maturation. The results showed an important effect of environmental factors on the ripening progression based on the agronomic fruit traits and phenolic fraction. Differences in the technological use of olive fruits were observed among samples of different origins. The phenolic compounds of 25 olive samples were analyzed by HPLC-DAD-ESI-MS/MS, and 9 phenolics belonging to different families of phenols were identified and quantified. The harvest time and the geographical location were observed to interact and quantitatively govern the phenolic compounds production during maturation of olive fruits. Gemlik olive phenolic compounds can be used as a marker of each growing area and as a predictor of the optimal harvesting date, to optimize the organoleptic and nutritional value of the end product.