Power systems have been conventionally involved with uncertainty and variability due to unpredictable network component contingencies. Recently, large penetration of variable generations has made this variability even worse than before and drives a need for greater flexibility. This paper proposes a flexible security-constrained framework which coordinates supply-side and demand-side in an appropriate way to meet the need for this greater flexibility toward a secure, economic, and green power grid. In the proposed model, conventional units are contributed to flexibility enhancement through providing up and down operational reserves while demand-side flexibility is enabled via an optimal TOU (time of use) pricing scheme as a most prevalent time-based rate demand response programs. Since increasing the share of renewable resources reduces the electricity market prices, it may lead through a situation in which customers do not have enough tendencies to response in expose to the TOU rates. Hence, the paper concludes with determination of optimal TOU tariff rates in the face of high penetration of wind power as well as network contingencies. (C) 2015 Elsevier Ltd. All rights reserved.