This article is concerned with characterizing literacy activity as it is practiced in professional workplaces. Its starting point is activity theory, which grew out of the work of Vygotsky and has been subsequently elaborated in Russia and elsewhere. First, the authors propose that existing versions of activity theory are unable to account adequately for practical human activity in contemporary workplaces, and present a revised perspective that opens the way for new theoretical developments. Second, they elaborate two new constructs, task and work ensemble, and apply them to a short collaborative writing sequence collected in the field. Both constructs are seen to account in a substantive way for the structure of the composing activity carried out by the collaborators. They close with a discussion of the complementarity and theoretical advantages of the two constructs.