This paper presents a novel formulation for multilayer composite generation and transmission expansion planning considering the high penetration of wind farms. The proposed approach employs the so-called two-stage stochastic programming to cope with the uncertain nature of load demand and wind power and then find the optimal expansion plan among candidate generating units and transmission lines through the minimax regret criterion. Finally, the proposed approach is implemented on 24-bus reliability test system and the effect of the number of scenarios on the computational burden as well as the final optimal solution is evaluated.