To deliver multicast messages reliably in a group, each member maintains copies of all messages it sends and receives in a buffer for potential local retransmission. The storage of these messages is costly and buffers may grow out of bound. Garbage collection is needed to address this issue. Garbage collection occurs once a process learns that a message in its buffer has been received by every process in the group. The message is declared stable and is released from the process's buffer. This paper proposes a gossip-style garbage collection scheme called GSGC for scalable reliable multicast protocols. This scheme achieves fault-tolerance and scalability without relying on the underlying multicast protocols. It collects and disseminates information in the multicast group by making each group member periodically gossip information to a random subset of the group. Extending the global gossip protocol further, this paper also investigates a local gossip scheme that achieves improved scalability and significantly better performance. Simulations conducted in a WAN environment are used to evaluate the performance of both schemes.