Table olives are traditionally harvested manually. However, a shortage of agricultural workers and high labor costs have prompted the search for mechanical solutions. Mechanical harvesting of four cultivars of green table olive—Manzanilla, Hojiblanca, Souri, and Nabali Mouhassan—was compared with manual picking in terms of harvest efficiency and final product quality. Mechanical harvest methods were: trunk shaking with and without simultaneous rod beating and with and without the application of an abscission agent. Olives were immersed in a diluted NaOH solution in the field, transported to the processing plant, and subjected to commercial procedures processing. Application of an abscission agent resulted in inconsistent fruit-detachment force values and did not affect harvest efficiency. Mechanical harvest with rod beating reached high harvest efficiencies of 80% to 95%, whereas the elimination of rod beating significantly reduced harvest efficiency. Final product quality of the mechanically harvested ‘Hojiblanca’, ‘Souri’. and ‘Nabali Mouhassan’ was similar to that of their manually picked counterparts, whereas that of cv. Manzanilla was inferior to those picked manually. High harvest efficiencies can be obtained using trunk shakers and simultaneous rod beating but final product quality of the mechanically harvested olives depends on variety. In some, mechanical harvesting can be used safely; in others such as cv. Manzanilla, further work is required to obtain a good-quality final product.