Solar box cookers and solar panel cookers normally do not need to be turned to follow the sun unless you are cooking beans or an especially large amount of food. If tracking the sun is necessary, some of the ideas below might serve this purpose.
Still in its infancy, programable tracking systems are being developed with software to not only rotate the reflector to maintain maximum exposure to the sun, but to also control cooking time and desired temperatures.
December 2010: Programable system tracks the sun, and turns the reflector away when cooking is completed.
Audio and video
March 2011: Box cooker rotated by PV panels sending power to 12 volt motor. As one PV panel begins to receive less light, it sends less power to the servo, which operates the motor until both panels are a sending balanced power stream.
April 2010: UC Berkeley student tracking system demonstration