Grid computing is an emerging computing paradigm that will have significant impact on the next generation information infrastructure. Service description and discovery play a key role in the service-oriented Grid architecture. The federation of highly distributed heterogeneous resources to deliver better-than-best-effort services is the key feature of Grid applications. Therefore, networking systems with Quality of Service (QoS) provisioning capabilities form the basis for high-performance Grid applications. The underlying networks should be integrated into the Grid architecture as services in order to be effectively utilized by Grid applications. However, current Grid service description and discovery technologies are not sufficient to support the network QoS required by high performance Grid computing. In this paper, we propose a new description approach for Grid network services and develop a QoS-based service discovery technique that discovers the network services that meet the QoS requirements of Grid applications. Our approach can be implemented within the current Grid service discovery framework.