In this paper, solar box cookers with ordinary and finned absorber plates are theoretically investigated in terms of thermodynamic performance parameters. For a typical summer and winter day, temperatures of solar cooker components such as glass cover, internal air, absorber plate, cooking vessel and the liquid are determined theoretically versus time. The analysis is carried out for conventional and finned absorber plates, and accuracy of the results is verified by a previously published experimental work. Energy and exergy efficiencies of box-type solar cookers are plotted versus time for various cases. The methodology presented in this paper enables to make a preliminary evaluation of ordinary and modified solar box cookers with respect to changes in main environmental parameters such as temperature and illumination intensity. Some recommendations are also made to enhance the power outputs of the aforementioned solar cookers.