Using conversation analysis and situated learning theory, in this paper we analyze the peer dyadic interactions of one adult learner of English in class periods 16 months apart. The analyses in the paper present microgenetic and longitudinal perspectives on the learner's increasing participation in his classroom communities of practice. The focus of the analyses is on the language practices for a social action that is not taught explicitly by the instructors—disengaging from teacher-assigned dyadic task interactions. The tasks from which the learner disengages are serial dyadic interaction tasks. In these tasks, a learner engages with a number of different classmates doing the same task consecutively. The serial dyadic interaction task design is shown to offer students ongoing opportunities to develop interactional routines for social actions and language practices needed to accomplish habitual actions such as opening and disengaging from their dyadic task interactions.