Abstract. From the recent past and current state of the Internet, it is possible to forecast a wide growing of Multi Organizational Web-based Systems (MOWS). Therefore, the reduction of both costs and time-to-market is desirable. On the other hand, the success of building software in Product Lines (PL) is being demonstrated in different contexts reducing both time-to-market and costs. However, research on PL topics has not been oriented to include web-based assets. In this article, we propose a first approach to use PL methodologies to build MOWS. We identify quality aspects as a key point when building Product Lines of MOWS and we give a way to specify quality aspects in PL.