Our paper addresses the representation of territorialized and conflicting interests by the Members of the European Parliament (MEPs) through a case study on the posting of workers. Public debates on the reforms to the legal framework for this controversial practice have been steadily increasing since the EU's eastward enlargement. Focusing on parliamentary questions, our mixed-methods research design analyses why and how MEPs take position on this highly divisive issue, beyond their nationality and a so-called opposition between Eastern and Western EU member states. MEPs' implication depends both on the impact that the posting of workers has on employment in their home country and on their own political career, including whether they hold national or local electoral mandates. These factors also determine which political roles are performed by MEPs (moral entrepreneur, policy maker, interest groups broker), as the textual analysis of their questions in Parliament highlights. These results emphasize the influence of parliamentary socialization on the positions taken in the debates about social Europe, but also the significance of the territorial dimension of parliamentary representation.