The article proposes optimal secondary controller for combined Load Frequency Control (LFC) and Automatic Voltage Regulation (AVR) of multi source multi area system using simulated annealing technique. When subjected to load disturbance, frequency, tie-line power and voltage fluctuations results higher oscillations. Speed governor of the system helps to match generation with the demand. But, fine tuning of frequency, tie-line power and voltage when subjected to load disturbance in multi source multi area system is achieved by secondary Proportional Integral Derivative (PID) controller. As a conventional benchmark PID controller is tuned using Zeigler Nichol's (ZN) method and further optimized using Simulated Annealing (SA) technique. The performance of the system is validated and judged using performance indices. (C) 2015 Elsevier Ltd. All rights reserved.