This study aims to explore what ambitious mathematics instructional practices are carried out in the classroom during a national-scale mathematics teacher professional development program and investigate the variability in use of those practices. By using data from 174 video-recorded lessons that were coded with the UTeach Observation Protocol, lesson profiles that represent typical instructional styles enacted during the program are characterized. Overall, lessons typically included ambitious mathematics instructional practices related to lesson structure (e.g., the mathematical tasks used in the lesson) rather than teachers' classroom actions (e.g., their moves to involve students in the lesson). Moreover, the results from a cluster analysis show four different lesson profiles with large variations in relation to which ambitious mathematics instructional practices are included, to what extent and with what quality. Based on the study's results, possible sources for variability are suggested, including class size and parents' level of education.