In a MIMO-based ad hoc network, the conflict relation between transmissions is fundamentally changed due to the multiple packet reception capability of MIMO nodes. A MIMO node can receive from multiple data streams at the same time, which significantly increases data throughput. To fully utilize the additional spectrum capacity enabled by the MIMO technology, it is important that transmissions from different nodes are coordinated. The coordination scheme needs to consider both data stream multiplexing and transmission time scheduling for a maximum performance gain. In this paper, we use an optimization framework to jointly consider MIMO link spatial multiplexing and scheduling while the routing information is given. A linear program-based algorithm is proposed, and simulation results show it is advantageous over the spatial multiplexing scheme without joint design of scheduling.