Researchers have stressed the importance of argumentation among small groups of students in STEM courses to help them develop deep understanding. But it is not widely used in college courses due to such challenges as finding time in already packed courses, effective organization of argumentation in large classrooms, etc. This paper presents a novel online approach to enable argumentation to be adopted widely. One interesting question we investigated in a junior-level computing course concerned the structure of such arguments. Common experience with online forums in courses suggests that a handful of students dominate them while others hardly participate. So we expected that round-based discussions where each student in the group made one submission in each round, the submission not being available to the others until the start of the next round, would be more effective than forum-based discussions where students made submissions whenever they wished to and saw each submission as soon as it was made. But our results showed that both were equally effective! We present the details of our approach, the unexpected results from our course, some hypotheses that may explain the results, and future plans to investigate this anomaly further.