In France, efforts to strengthen the citizen-government nexus and their collaboration initially focused on service delivery. Recent initiatives, however, have emphasized policy design and online solutions targeting collaborative governance. This turn to e-participation for policy design is embedded in the context of support for an open government, with France joining the Open Government Partnership in 2014. Since then, e-participation platforms for policy design have flourished, mostly at the local level, but also at the national level. The highly covered Law for a Digital Republic in 2015, where citizens could directly participate in the drafting of the law through an online platform, is a clear, though one-off, instance of online collaborative policy design.This chapter takes on the task of contributing to the study of online collaborative policy design in France by investigating the sole longstanding e-participation platform for law-making that exists at the national level: Parlement & Citoyens -'Parliament and Citizens' (P&C) (see https:// parlement -et -citoyens .fr/ ). P&C is a platform connecting citizens and legislators to make them work together to draft policy proposals. Legislators are invited to upload draft laws on the online platform, which is open to the comments and votes of citizens and organizations. The case of P&C differs from most of the initiatives analysed in this volume in three ways. First, P&C is a private initiative. The platform was launched bottom up by individuals concerned with democratic issues. Second, P&C is intended to tackle national policy issues, not local or regional matters. And third, the platform aims to connect citizens with legislators, rather than with actors of the executive branch.In this chapter, a supply-side perspective on the e-participation platform is adopted. A wide range of studies have contributed to the study of the participants of online collaborative platforms and the process of participation as such, thereby exploring the demand side of online collaborative policy design (Gerl et al., 2018;Lutz and Hoffmann, 2017;Rasmussen and Carroll, 2013). Along with other chapters in this edited volume, the attention is shifted to the thus far mostly overlooked organization of e-participation platforms. Specifically, the chapter relies on an institutionalist perspective to analyse how the organizational features of P&C shape the participation of critical actors, the legislators themselves and citizens, as well as the outcomes of e-participation on the design of policies.