New social networking and social web tools are becoming available and are easing the process of customizing online social environments for enterprises. With these developments, core design efforts have been extending beyond usability for individual users and are beginning to include notions of sociability for the engagement of communities of users. In an effort to make it easier to design for social engagement in an online social environment, the authors developed a domain-community model based on the communities-of-practice concept and the work domain analysis used in cognitive work analysis. Through a case study of University-Community Partnerships for Social Action Research, an international development leadership community of practice, the authors illustrate how the domain-community model could be used to design web components of an online social environment that integrate internal issues of social engagement and external issues of domain effectiveness. It is expected that this model can provide a basis for designers of online communities to more systematically account for social phenomena of collective efforts in a given work domain.