In recent years, researchers from a Vygotskian Sociocultural Theory (V-SCT) perspective have sought to promote and trace the development of both emotion and cognition. Contributing to this emergent body of research, our study leveraged Concept-Based Language Instruction (C-BLI) and a Division-of-Labor Pedagogy (DOLP) to investigate the second language (L2) literacy development of university, intermediate level French learners (Buescher, 2015; Urbanski, 2023). Through investigating mediation by a researcher-teacher and in a collective, we traced four learners' emotional and cognitive development by examining the overall content as well as micro-interactional features of their contributions to the group both on a moment-to-moment basis and over the twelve-week span of a literacy intervention. We found that the DOLP, an instructional arrangement where each group member has a key role to play in promoting the collective's meaningful engagement with texts, not only supported the development of learners' literacy abilities but also created the conditions for peer emotional mediation and development. This study has implications for language researchers and practitioners, compelling us to reflect on how we ask learners to collaborate and what kinds of development that collaboration allows.