In this paper, we investigate a joint scheduling and power control for a multi-cell cognitive radio network (CRN) in coexistence with a cellular primary radio network (PRN). The PRN uses a set of licensed orthogonal channels for transmission. This set of channels is also accessed in an opportunistic manner by a set of cognitive radio base stations (CR-BSs) to support secondary users (SUs). The problem is formulated to maximize the spectrum utilization of SUs without causing excessive interference to active primary users (PUs) of the PRN. In addition, all the served SUs must meet a certain QoS. A centralized solution for joint scheduling and power control is derived to give the global accessing decision for all unserved SUs. With the assumption that the knowledge of all subscribers is available, the coordinator of the CRN can use the joint scheduling and power control algorithm to maximize the spectrum utilization of served SUs by solving a mixed-integer linear programming (MILP) with an NP-hard complexity. To avoid the NP-hard complexity, we propose a sub-optimal heuristic algorithm that can be obtained at a much lower complexity based on the coloring interference graph among unserved SUs effected by served SUs and active PUs. Simulation results show that the proposed algorithm can yield the performance close to the optimal solution's.