SOC (service oriented computing) becomes a hot topic of research recently because it accelerates rapid application development by service reuse. Delivering end-to-end QoS (quality of service) in SOC environment is a critical and significant challenge. QoS is modeled for a single service based on this view: quality is seen as conformance. Then, QRGM (QoSResource Graph Model) is adopted for service composition. An illustrative example is used to account for how to model end-to-end QoS in service composition using QRGM. At last, QRGM is compare with other current common service composition models. Conclusion is made that QRGM provides better support for QoS than other service composition models.