A solar combination unit was developed be suitable for cooking and water desalination. Ordinary solar box cooker was developed to be accommodate for desalination and cooking. Different configurations were carried out under study as: Cooker without mirror reflector (C1), Cooker with mirror reflector (C2), Cooker integrated with flat-plate solar collector (C3) and Cooker integrated with mirror reflector and flat-plate solar collector (C4). Fourth merit figure and overall thermal cooking efficiency were applied under water load densities of 1.0, 1.5, 2.0 and 2.5 L to select the highest system performance. Preliminary experiments clarified that using C4 system and 1.5 L of water gave the highest efficiency compared to other treatments. Thermal analysis was done based on internal and external heat transfer to predict the used C4 behavior. The performance evaluation was conducted as a function of change in different brine depths of 1, 2 and 3 cm under conditions of groundwater desalination, cooking rice (T1), potato (T2), cake (T3) and egg + potato + rice (T4) and desalination-cooking combined systems. This is in terms of system productivity, internal and instantaneous thermal efficiencies and cooking time. Experimental results revealed that the use of desalination-cooking combined system gave the highest distillate water productivity (9.38 L/m2•day) as well as internal and instantaneous efficiencies (60.17 and 41.43%), added to that decreased the cooking time; T1 (39 min), T2 (43 min), T3 (49 min) and T4 (100 min) under condition of 1 cm brine depth.