In this research note, we propose studying a new trend of Europeanisation in national parliaments within the European Union (EU). We argue that further integration, combined with the opportunities and challenges presented by the Lisbon Treaty and the financial crisis, created pressure on national parliaments to expand the scrutiny process beyond European Affairs Committees. In this new phase of Europeanisation, parliaments are increasingly 'mainstreaming' EU affairs scrutiny, blurring the distinction between national and European policies and involving larger numbers of MPs. Following a review of existing research on the Europeanisation of national parliaments in the post-Lisbon era, we propose studying four dimensions of mainstreaming: the rising involvement of sectoral committees in European affairs; the adaptation of parliamentary staff to EU policy-making; the growing salience of European affairs in plenary debates; and increasing inter-parliamentary cooperation beyond European affairs specialists. We argue that this trend has significant implications for research that studies the roles of national parliaments in the democratic functioning of the EU.