Solar heating is a promising technique for controlling stored product insect pests. In this study, we investigated the effect of a solar heating system at different exposure times (0, 5, 10, 15, 20 and 30 min) on different developmental stages of Trogoderma granarium (Coleoptera: Dermestidae) and Stegobium paniceum (L.) (Coleoptera: Anobiidae) on wheat. Exposing wheat to 75 °C for 20 min resulted in complete mortality of adult beetles for both species. Solar heating for immature stages (eggs, larvae, and pupa) resulted in complete suppression in adult emergence after 15 min at 70°C and after 20 min at 75°C in both species. From the bioassay, the pupal stage was the most tolerant stage to solar heating. The effect of solar heating on the two antioxidant enzymes peroxidase (POD) and glutathione S-transferases (GSTs) as well as the total protein amount was also investigated. The total protein content of the larvae of T. granarium and the adults of S. paniceum exposed to solar heating was significantly lower than the total protein of the parallel control samples. Furthermore, there was a highly significant difference in GST and POD activity between the control and treated samples in both species. In addition, the viability of the wheat grains was not affected by heat treatment. Thus, solar heating is recommended as an effective alternative to chemical control for stored grain insect management.