This paper presents a security constrained unit commitment (SCUC) suitable for power systems with a large share of wind energy. The deterministic spinning reserve requirement is supplemented by an adjustable fraction of the expected shortfall from the supply of wind electric generators (WEGs), computed using the stochastic feature of wind and loosely represented in the security constraint with scenarios. The optimization tool commits and dispatches generating units while simultaneously determining the geographical procurement of the required spinning reserve as well as load-following ramping reserve, by mixed integer quadratic programming (MIQP). Case studies are used to investigate various effects of grid integration on reducing the overall operation costs associated with more wind power in the system.