The debate on whether and how to structure collaboration in online learning environments is quite active. In this paper the authors identify Task, Team and Time as the main components of an online collaborative activity, through which the overall structure of the activity can be determined to scaffold learners\u27 interactions. Based on five examples of real-life online learning activities featuring different degrees of structure as to Task, Team and Time, the authors reflect on the extent to which the way these three dimensions are structured may affect the overall learning process. Method of the study is interaction analysis of the students messages, exchanged in asynchronous mode during the activity. The analysis was carried out according to a quantitative and qualitative model that distinguishes among the participative, social, cognitive and teaching dimensions. The results of the study seem to support the hypothesis that the three Ts well represent the structure of CSCL activities and that, in many cases, it is the lack of structure in one or more of them that is associated to a higher frequency of some indicators, as if the missing guidance causes an enhanced effort on the side of the learners to compensate the deficit
