In this paper, we explore the problem of scheduling multiple concurrent Bag-of-Tasks (BoT) applications in unstructured peer-to-peer (P2P) volunteer desktop grids built around a super-peer framework. Resource availability information is exchanged among the super-peers using a light-weight thresholddriven gossip protocol with the aim of minimizing the resource discovery overhead. We present a comprehensive study of the properties of fixed threshold and adaptive threshold based gossiping mechanisms using detailed simulation experiments.Our results indicate that while gossiping with fixed threshold reflects resource usage effectively in a scalable network, an adaptive gossip threshold mechanism based on a simple feedback mechanism considering system state adapts much better to a volatile environment with small latency, reduced overhead and yields better system performance compared to fixed threshold protocols.