In this technical note, we consider the cooperative output regulation problem for linear multi-agent systems subject to communication delays and switching networks by a distributed feedforward approach. Both distributed dynamic state feedback controller and distributed dynamic measurement output feedback controller are proposed to solve the problem. In comparison with the existing result for the similar problem, our result can handle the cooperative output regulation problem subject to nonuniform time-varying communication delays and jointly connected switching communication networks. As an application of cooperative output regulation, it is shown that our main result can solve the leader-following consensus problem and includes some existing results as its special cases.