Collaborative partnerships between families and teachers have the potential to support and transform students' mathematics learning experiences. This study focused on interactions among mothers and teachers of multilingual elementary grade students who participated together in workshops focused on teaching and learning mathematics. We analyzed participants' engagement in open-ended, culturally responsive mathematics tasks designed to foster collaboration and equitable participation. We describe several findings related to the potential of these tasks, including how they supported opportunities a) to recognize one another's strengths; b) to challenge traditional power differentials between parents and teachers, and c) to collaboratively generate mathematical ideas. We also discuss challenges that arose, and implications for the design of collaborative learning experiences for teachers and parents. [For the complete proceedings, see ED658295.]