In this study, the minimum quality loss of 2-phase olive pomace and the maximum system's energy efficiency is targeted during pre-drying of olive pomace in a drum dryer. Vapor pressure and valse rotational speed were selected as the independent variables of drum dryer. For each vapor pressure value (1, 2, 3, 3.5 and 4 bar), drying of 2-phase olive pomace was performed at different valse rotational speeds (0.5, 1, 2, 3, 4.5 and 6 rpm). Drum dryer conditions were optimized with desirability function approach by targeting the moisture content range as 30-50%, minimum peroxide value and maximum specific moisture extraction rate (SMER). The optimum drum dryer conditions were determined as 3.27 bar for vapor pressure and 6 rpm for valse rotational speed. Moreover, the effects of vapor pressure and valse rotational speed on the physical and chemical properties of pre-dried 2-phase olive pomace and the system's energy efficiency were examined.