This paper presents a scalable overlay multicast congestion control scheme (OverlayTFMRC) for multimedia streaming over Internet. The scheme seeks to extend multicast scalability within our previous TCP-Friendly unicast congestion control scheme streamTFRC using multiple time-scale prediction for multimedia QoS transport. Besides efficient QoS transport support based on our previous work, Over-layTFMRC implements multicast scalability design into session rate control, feedback compression and data forward respectively by fully considering overlay network characteristics. Compared with TFMCC, simulation experiments illustrate that our scheme achieves not only better session scalability performance in terms of session throughput and its smoothness, but also better TCP-Friendly performance in terms of intra-protocol& inter-protocol fairness and smoothness.