The literature on lobbying coalitions has explored the choice of interest organizations to cooperate with others in a series of correlational studies. Yet, considerable diversity in cooperation activities, as well as path dependencies between organizations complicate these analyses. For this reason, we still have limited knowledge about different types of asymmetries between coalition partners that inform organizational cooperation. Experimental studies can add to these findings by assessing differences between the strategic choices made by organizations in more controlled, though hypothetical, settings. In this article, we present the results of a preregistered survey experiment, conducted in eight European polities (Denmark, Sweden, Germany, Austria, Ireland, The Netherlands, Italy, and the European Union) to understand the willingness of organizations to cooperate with âstrangers,â as well as members of their network in the agendaâsetting phase of policymaking. We also test the willingness to cooperate with different types of groups (NGOs and business organizations), and gauge how treatment effects vary for different types of respondents. Our results help understand the importance of previous connections, homophily and reputational considerations in coalition formation in the policy process. Moreover, our study uncovers differences in the willingness to engage in different types of cooperation and indicates that inequalities exist between interest organizations when it comes to partner choice that we so far know little about.