This dissertation on the Economic, Social and Environmental Regional Councils (Conseils économiques, sociaux et environnementaux régionaux, or CESER) aims at addressing the question of how such assemblies can operate the intermediation of different institutional universes within the regional public space. Such consultative socio-occupational assemblies constitute an area where transversal exchanges between policy-makersand interest groups representatives from contrasting universes are realized, through the collective elaboration of opinions and reports destined torepresent the interest and to produce expertise on the public problems of the regional government. In addition to its formal, yet limited, role ofconsulting socio-economic interests as part of the decision-making process of the Conseil regional, the CESER plays a role in structuring andinstitutionalizing the interest groups at the regional level, and in disseminating the shared representations that result from its deliberations.