In order to capitalize on its increasing legislative powers, the European Parliament (EP) has had to specialize internally. The scholarly literature has predominantly studied the structural manifestations of specialization, such as the allocation of committee seats among parliamentarians. This article sheds light on a second selection process: participation in legislative negotiations. For every given legislative dossier, parliamentarians have to decide whether and how strongly to participate in the negotiations. The literature on office allocation contains assumptions about the role of office-holders in negotiations. The first aim of this article is to test the validity of these assumptions. The second aim is to apply theories used in studies on office allocation to negotiations and gain insight into the following questions: Are actors with extreme preferences more active than others? What is the role of experts? How do party politics play out? Although we find effects of preferences and expertise on negotiations, the evidence is most compatible with the view that negotiations serve EP party groups to form and exchange policy positions.