This paper deals to find the dynamic response of load frequency and corresponding tie-line power of an automatic generation control (AGC) in four area interconnected thermal power system by using two different technique (Controller); One is Intelligent (Fuzzy Logic Controller) technique and second is Evolutionary (GA for tuning of PID Controller) Technique. In this paper evolutionary technique are proposed for improving the performance of load frequency and tie-line power and their dynamic responses are compared with the intelligent controller’s responses. The results indicate that the proposed controller exhibit better performance and satisfy the automatic generation control requirements with a reasonable dynamic response. The performances of the controllers are simulated using MATLAB/SIMULINK software. © 2015, School of Electrical Engineering and Informatics. All rights reserved.