As second-language (L2) classrooms embrace technology for learning through computer-mediated communication, there is need to consider how L2 learners can learn online collaborative techniques when traditional teaching methods have not encouraged online collaborative skills. This qualitative study examines how post-secondary English language learners (ELLs) at an English language institute in a large research university work as groups within their levels of language proficiency (i.e. beginning, intermediate, and advanced) to complete online writing assignments using wikis. Through linguistic and directional scaffolding, the wiki writing assignments include frequent word sequences for language support and specific writing instructions that promote interaction and collaboration among members. A grading rubric was also designed and implemented to evaluate not only the ELLs' writing but also group collaboration -- resulting in group scores instead of individual scores. The results indicate that, despite providing ELLs scaffolding in collaboration and English writing, learners in the study continued to face challenges with participation through collaboration and focused on negotiating meaning rather than spelling and grammar.