The responses of oregano plants to water limitation from soil and seasonal phenological cycle are not fully understood yet. The aim of the present research was to help understanding the production of oregano essential oil and biomass facing soil water deficit, which was studied in different seasons. Oregano was subjected to drip irrigation, the water deficit being assessed in the vegetative and pre-flowering stages, as well as whole cycle analysis, through water matric potentials in the soil. The matric potential -60.8 kPa adopted in the irrigation handling during the oregano cultivation interval, led to higher essential oil content and yield. The same potential applied during the oregano pre-flowering stage resulted in the best mean of oregano fresh biomass production. The best dry biomass production was reached by using the matric potential -91.2 kPa in the oregano pre-flowering irrigation management. Water restriction in the soil throughout the entire phenological cycle favored essential oil production, whereas the water restriction during the pre-flowering stage enabled high oregano dry biomass production. The highest values for biomass and essential oil productions were reached for the oregano plants cultivated during spring/summer.