In this article we use a sociocultural framework to suggest task engagement as a viable construct in L2 learning research. Clarifying and specifying this construct has important implications for the analysis of conversational data, needed in light of claims for the causal relationship posited for certain kinds of conversational adjustments on L2 acquisition outcomes. Here we examine L2 learner data to identify task engagement as it emerges, unfolds in dialogic activity, and becomes associated with the transformation of task, self, and group. The data to be analyzed come from two pairs of L2 learners involved in jigsaw tasks, one pair using Swahili, the other Spanish; all are native speakers of English. Our concern with task engagement is motivated by methodological and theoretical issues entailed in the study of L2 learning in the interactionist perspective. We argue that a sociocultural approach offers an alternative to that perspective, from the standpoint of method and theory, resting as it does on quite a different set of underlying assumptions, to be described below. The research questions are the following. (1) How might task engagement be defined within a sociocultural framework? (2) What is the effect of task engagement on data analysis and interpretation? (3) What transformative effects, if any, can be found during task engagement? In the first section we juxtapose the two frameworks for thinking about task performance, demonstrating that certain phenomena not even considered data according to one perspective can be interpreted as crucial in selecting, analyzing, and interpreting data in the other. We go on to present and interpret the task data using the proposed analytic framework, then draw conclusions based on the findings.