Online tools, such as forums, wikis, and blogs lend themselves to learners negotiating meaning and co-constructing knowledge through interaction. However, not enough is known about how tasks need to be designed to make best use of the possibilities of complex virtual learning environments (VLEs) to motivate and support learners, foster interaction, and contribute to knowledge construction. This article reports on a two-year study exploring the design and implementation cycle of online activities as an integral part of a distance language course. When the course was introduced in 2009, activities had been designed on the basis of second language acquisition principles as well as sociocultural theories, providing a basis for student interaction and taking into account the affordances of the environment, a Moodle-based VLE. After the end of the first year an evaluation was carried out that examined quantitative and qualitative data (Moodle user logs, learner survey and learner interviews). It was found that students preferred forums to other tools and that assessment-related activities attracted higher participation rates than other tasks. It also highlighted a number of issues, including low participation in on-task discussions, a large gap between viewings and contributions, very large differences in individual engagement, low priority given to the online activities by some students, and varying levels of e-literacy amongst learners. Consequently, activities were re-designed and a number of changes were implemented in 2010 that included more teacher involvement, fewer tasks, a simpler structure, and a reduced number of tools. A comparison of learner participation across the two years shows that these changes had a positive impact on learner engagement.