CSCL systems can benefit from using a grid, since it offers a common infrastructure allowing an extended pool of resources that can provide supercomputing capabilities as well as specific hardware resources. Adopting a service oriented architecture such as OGSA can further benefit CSCL systems, enabling increased flexibility to adapt and reuse learning software. However, proliferation of services enormously challenges the search of appropriate ones. Common service discovery mechanisms, such as the Index Service or UDDI, perform poor searches since they rely on keyword matching and do not properly describe service functionality. To address these difficulties, ontologies can be used to formally describe services allowing for semantic searches. This paper proposes an ontology that describes learning services using educators abstractions in order to support the search. This way, service providers can describe their services in terms of the ontology, while educators can search for them using domain concepts. The integration of this enhanced service search mechanism in Gridcole, a real grid-based CSCL system, is described to illustrate its performance.