This study examined the experiences of 13 graduate students enrolled in a closed, lock-step master's degree of the education cohort program. Interview and observational data, collected over 10 months and across four courses, were qualitatively analyzed to explore students' understanding of the meaning of cohort membership and how that membership both shaped their educational experience and the development of peer and instructor relationships. Results indicate that both the meaning and influence of cohort membership were fluid and evolved as students progressed in their program, changing from an inconsequential to a significant meaning and from a modest to a deep influence.