This dissertation presents a multiple tabu search (MTS) algorithm to solve the load frequency control (LFC) and the economic dispatch (ED) problems in power system operation. The proposed MTS algorithm is the sequential execution of the individual tabu search (TS) algorithm by only one personal computer. MTS algorithm introduces additional techniques for improvement of search process, such as initialization, adaptive searches, multiple searches, replacing and restarting process. For LFC application, the proposed MTS algorithm has been applied to design a fuzzy logic controller using a proportional-integral (FLPI) and a proportional-integral-derivative (FLPID) for load frequency control. Conventionally, the membership functions and control rules of fuzzy logic control are obtained by trial and error method or experiences of designers. To overcome this problem, the MTS algorithm is proposed to simultaneously tune PI or PID gains, the membership functions and control rules of the FLPI or FLPID of fuzzy controller. The objective of the designed controller is to minimize the frequency deviations of the interconnected power system against load disturbances.