Museum partnerships can involve significant tensions, especially when these collaborations reach across institutions to blend disciplines such as art and mathematics. Rather than simply being obstacles to overcome, we suggest that tensions arising in multi-institutional, cross-disciplinary collaborations can be highly generative for collaborators, sparking new approaches to practice and catalyzing professional growth. To support this idea, we describe an interdisciplinary professional development program for museum practitioners focused on developing innovative programs and exhibits integrating Science, Technology, Engineering, Art, and Mathematics (STEAM). We discuss the design of this STEAM Professional Learning Laboratory in terms of a shared-facilitation model and relate that model to specific tensions that arose in this collaboration. Based on evaluation data, we summarize key characteristics of the Lab that supported successful collaboration and interdisciplinary learning. We share learning outcomes we documented for art and science museum professionals who participated in the Lab. We conclude with considerations for others in the field engaging in similar efforts. A bibliography is included.