This paper addresses two drawbacks associated with using SOAP RPC to invoke services in service-oriented environments. First, overlapping of parameter production, parameter transmission and service execution is not possible, since all parameters of a service call have to exist prior to service invocation; until all parameters are available, a service caller has to defer service invocation. Second, the XML format of SOAP is not suitable to transfer large binary parameters, because encoding consumes a considerable amount of time. In this paper, a new approach to invoke web services is presented, which enables post-invocation parameter transmission and efficient transmission of binary parameters, thus enabling the overlapping of parameter production, parameter transmission and service execution to reduce the overall processing time. To realize post-invocation parameter transmission, an extension of WSDL is proposed. It is shown how post-invocation parameter transmission enables the efficient implementation of streambased production/consumption of parameters and pipelining. Furthermore, measurement results are presented demonstrating a noticeable performance gain.