Vocational education and training (VET) is intended to prepare adult learners for careers that are based on practical activities. With the underlying constructivist andragogy, this study intended to examine the effects of computer-mediated group collaboration in vocational education, and how that affects the associated learning outcomes. For collaborative learning, use of asynchronous computer-mediated communication as one of the major media prevails not only in web-based formats but in face-to-face. Specifically, our intent was to explore effectiveness of asynchronous online discussion (AOD) and the learning outcome accordingly. The results provided evidence that the participants in the AOD performed substantially better than those with no use of AOD in the bi-weekly quizzes as well as the learning outcomes. As incentive styles come into play, we found that the introverts performed as well as the extroverts disregarding the AOD participation. The results concluded that use of group collaboration as andragogical strategy (use of AOD) inferred better learning outcomes in the context of VET. (Contains 2 tables.)