(Free to download through January 2020): Recent research emphasizing disciplinary identities in the classroom indicates the importance of social interaction and inclusion in the classroom, yet only limited work focuses on how peer-initiated exclusion impacts learners. This study addresses that gap by examining the role of microexclusions, or affronts to sense of belonging and competence, in collaborative groups in 7th grade inquiry science classrooms. The qualitative analyses here involved videorecorded observations for 5 small groups of students participating in a semester-long series of inquiry life science units. A total of 19 observations were analyzed across the 5 groups. Five themes were identified across the groups: individualization or splitting of the group, adversarial interactions within the group, uneven access to regulatory roles within the group, lagging group members, and using diffuse status characteristics to redirect group activity. Results indicate that microexclusions redirect learners' behavior toward managing participation dynamics inside the group at the cost of inclusion and group functioning. Implications for equity and science education reform are provided considering findings.