Technology-mediated task environments have long been considered integral parts of L2 learning and teaching processes. However, the interactional resources that the learners deploy to complete tasks in these environments have remained largely unexplored due to an overall focus on task design and outcomes rather than task engagement processes. With this gap in mind, we set out to describe the emergence, development, and diversification of L2 (English) interactional resources oriented to task completion using conversation analysis for the examination of 13 hours of screen-recorded online task-oriented interactions collected over 18 weeks. The focal tasks in the study have been designed as emergent information-gap tasks that require the participants to maintain progressivity by both displaying their own and converging with their co-participants' dynamic knowledgeability for task completion purposes. A longitudinal investigation into task engagement processes has demonstrated that the participants fail to display their knowledge congruently and they repeatedly disrupt the progressivity of task-oriented interaction in earlier weeks. However, an observable diversification of interactional resources for collaborative task accomplishment has been recorded in later weeks, which demonstrates the development of interactional competence over time. These findings bring insights into interactional competence, epistemics, and CALL with special reference to technology-mediated TBLT.