Many policy systems are experimenting with collaborative institutions to manage complex policy problems in the face of persistent conflict and scientific uncertainty. Policy networks are central to the theory of why collaborative institutions are effective. While many policy systems naturally become segregated, fragmented, or siloed due to homophily, collaborative institutions are hypothesized to create more integrated systems of organizational collaboration. Collaborative institutions may, therefore, be evaluated by the extent to which they reduce the tendency toward homophily and increase the integration of policy networks. This paper evaluates three collaborative institutions in regional land-use planning and specifies a theory of the program from two prominent frameworks: Institutional Collective Action and the Advocacy Coalition Framework. Results show that three forms of homophily are at work, and that in some cases, collaborative institutions successfully reduce the tendency toward network segregation.