In order for multi-institutional STEM education collaborations to scale justice-oriented change, the infrastructures they depend on must be designed--or redesigned--with equity and inclusion in mind. This article focuses on one interinstitutional collaboration as an example: the Sloan Equity and Inclusion in STEM Introductory Courses (SEISMIC) Project, which assembles 10 large public research-intensive institutions to study and promote equitable, inclusive STEM education. Referencing early lessons from SEISMIC, the authors discuss three domains where infrastructural design considerations shape how (and how well) interinstitutional collaborations advance equity and inclusion: people, voices, and data. Each domain involves design tensions and tradeoffs, highlighting the importance of understanding justice-oriented organizational (re)design as an ongoing process.