The article focuses on Teacher Time Outs (TTOs) in rehearsals and co-enactments as part of a practice-based approach to professional development, aiming to support teachers' learning of ambitious mathematics teaching. Ambitious teaching requires teachers to be responsive to students' ideas in-the-moment of instruction. This is complex and places enormous demands on the teacher. We examine how TTOs support teachers' learning of ambitious teaching and their development of pedagogical judgment. The findings reveal that the TTOs provided opportunities for teachers' collective learning of key practices of ambitious teaching, and that the TTOs supported the teachers' collective pedagogical reasoning and decision-making in-the-moment of teaching and with connecting pedagogical reasoning to pedagogical actions and responsibilities.