Organizations in the new millennium face relentless pressure to perform better, faster and cheaper, while maintaining high level of guaranteed results. To remain competitive, enterprises have to integrate their business processes with those of their customers, suppliers and business partners. Increasing collaboration is not only relevant within a global multi-national enterprise, but also considering the organization and its relationship to and business processes with its business partners. While standards and technologies make it possible for business partners to exchange information, collaborate and carry out business transaction in a pervasive Web environment, there is however very limited research activity on modeling business process outsourcing underlying semantics. In this chapter, we demonstrate that an in-house business process that has been gradually outsourced to third-parties and analyze how task delegations cause commitments between multiple business parties. Finally we provide process semantics for modeling multi-party business process outsourcing.