This paper focuses on the influence of task types, namely divergent and convergent tasks, on the interactional space of learners and the amount of collaboration in EFL adult learners' interactions naturally emerging from performing each type of task. To define interactional space, behavioural engagement measurement was adopted, and the total number of turns and words were quantified to define the distribution of learner talk in each task. Additionally, the categories of collaborative behaviours were quantified for both task types to illustrate their distribution in the tasks. The data of this study involve eleven hours of learner interactions collected from an EFL context where the learners voluntarily participated in a speaking club and completed eight tasks. The interactions were audio-recorded and used for the analysis of the influence of task types on learners' L2 production and the distribution of collaboration in each task. The results yield a difference in the amount of L2 production between tasks; for example, convergent tasks facilitate more L2 turns and more L2 words than divergent tasks although the mean length of utterance is higher in divergent tasks. Similarly, the distribution of collaborative behaviours is mostly higher in convergent tasks. The results are discussed in relation to both interactionist and sociocultural theories of L2 learning and some implications are also provided based on the results.