The purpose of this study was to optimize the performance of a double-exposure solar cooker based on exergy efficiency. Two similar solar cookers with variable parabolic mirror position were used for this experimental research. The system's exergy depends on many variables, which were kept fixed with the exception of the mirror position and operation time. The mathematical model of exergy efficiency was obtained based on the experimental variables, which could be used to optimize the mirror positions at any time. As a result, a new system with a variable mirror on a parabolic curve was developed, which can yield up to 30% increased mean exergy efficiency. Validation of the results was carried out by both the variance analysis test and comparing with the experimental data. The experiments were carried out in Mashhad, Iran, at 37 latitude, 54 longitude, and a height of 985 m above sea level.