In this paper, a fractional order proportional integral derivative (FOPID) controller for multiarea automatic generation control (AGC) scheme has been designed. FOPID controller has five parameters and provides two additional degrees of flexibility in comparison to a proportional integral derivative (PID) controller. The optimal values of parameters of FOPID controller have been determined using Big Bang Big Crunch (BBBC) search algorithm. The designed controller regulates real power output of generators to achieve the best dynamic response of frequency and tie-line power on a load perturbation. The complete scheme for designing of the controllers has been developed and demonstrated on multiarea deregulated power system. The performance of the designed FOPID controllers has been compared with the optimally tuned PID controllers. It is observed from the results that the FOPID controller shows a considerable improvement in the performance as compared to the conventional PID controller.