AbstractThis paper presents an investigation into patterns of interaction in synchronous, text-based computer-mediated communication (SCMC) with a focus on participation. The data constitute a corpus of 3,785 words from a series of interactions between student teachers performing learning activities in a three-dimensional online environment. Drawing on a systemic functional grammar perspective of language, we aim to develop a conceptual framework for understanding participation as made up of interactional patterns in students’ linguistic exchanges while performing learning activities. Our findings show that verbal negotiation that creates a shared understanding of what the group should accomplish or a common view of how to perform the activity is more frequent than strict activity organization. We argue that there are features of CMC signaling higher levels of complexity than those ordinarily found in face to face or written communication. The three broad interactional features identified – blending, turn-taking collaboration and delay endurance – corroborate our claim. This paper presents evidence that participation in text-based SCMC with learning purposes demands a disposition for collaboration and solidarity, a capacity to endure delay, and the ability to manage a conglomerate of information and communication tools without instructions on how-to processes.