In a previous research, a preliminary analysis on the thermal balance in different crushing systems for olive oil production was carried out. According to the previous results, in this paper the study has been extended to power consumption aspects related to the main quality features of the extracted olive oil, restricting the analysis only to the hammer crushing (Coratina cultivar), which represents the worst case. In particular, the effect of the olives delivery on the power consumption and quality of the extracted oil has been studied. The experimental trials, carried out on a laboratory plant during the 1993-94 and 1994-95 olive-oil seasons, show that, even though the diagram of power consumption has a parabolic increasing trend, the specific power decreases with the olives delivery. Anyway, studying the olives hammer crushing process also from the qualitative point of view (polyphenols number, acidity, peroxide number and induction time), it is possible to define an optimal range of olives delivery values. This optimal range (140 kg/h-240 kg/h for the studied hammer crusher) represents the better working solution from both the point of view of the power consumption and the quality of the extracted oil. In particular, at the beginning of the olive oil season it is necessary to work near the greatest lower bound of the optimal range just defined. With the passing of the harvesting time, the olives delivery has to be increased, reaching values near the greatest higher bound at the end of the olive oil season.