The rapid development of wind power generation imposes unprecedented challenges on power system operations due to its stochastic variations. This paper proposes the concept of dispatchable region (Disp-Reg) of the variable wind generation, and reveals its geometrical property. Disp-Reg is a polytope that indicates exactly how much nodal injected wind uncertainty a power system can handle. This concept can lead to a measure on the flexibility of economic dispatch strategies, or an extended version of the crucial concept “security region” in the uncertainty space. Moreover, this paper develops a systematic algorithm to compute the boundaries of Disp-Reg by solving linear programs and mixed integer linear programs. The PJM 5-bus system is used for illustrating the Disp-Reg concept. Finally, the proposed method is applied to a real power grid in China to demonstrate its practical implications.