Employing membership categorization analysis and conversation analysis, we uncover how students performing classroom discussion tasks for language learning locally ascribe themselves and others to various identity categories within single discussion activities. Data consist of 126 hours of video-recorded small-group discussions for second language learning collected in Japanese universities. Analysis unveiled the members' methods by which students themselves construct their identities in invoking various membership categories. In addition to sequential identities that are relevant at any point during the discussions, participants overwhelmingly oriented to hypothetical identities set up by the tasks. These identities were layered over the omnirelevant identities of Japanese language speakers, second language speakers, and students. Through publicly observable orientations to membership categories, these interactants manifested their collective understanding of the aims and motivations of the educational activities and institutional environment. The findings show how learners orient to their own and co-participants' multiple identities as they accomplish language-learning tasks and how these varied layers of identity contributed to language-learning affordances in different and unique ways. We then suggest some implications for task-based language learning.