It is known that to support a few common applications well, e.g., datacenter (DC) backup, multicast-oriented tasks need to be handled in inter-DC networks. In this letter, we propose an approach to schedule and route multicast-oriented tasks in inter-DC networks with arbitrary topologies. Specifically, we leverage Lyapunov optimization to develop a distributed online approach that can maximize the time-average profit with only local information. Besides, we also design a destination grouping scheme to address the scalability issue of our proposed approach and demonstrate that the number of queues in the system can be reduced significantly. Extensive simulations verify the performance of the proposed approaches.