Abstract: This study was carried out to enhance metacognitive abilities and skills of composing classroom action research proposal of the workshop participants of Teacher Profession Education (TPE). Subjects were participants of the workshop who were alumni of Biology Study Program of State University of Gorontalo, Manado State University and the University of Makassar. The study was conducted over 3 months from July to September 2014. The results showed that, the assessment of the portfolio as metacognitive strategies could enhance metacognitive skills of the workshop participants in developing a proposal of Classroom Action Research (CAR). The participant’s average metacognitive skill in the beginning was 78.8%. After the portfolio assessment as metacognitive strategy was applied in 8 sessions, it increased to 94.36%. The improved skill of developing classroom action research proposal after metacognitive strategy was implemented through a portfolio assessment was in Chapter 1, from 42.11-79.14%, Chapter 2, from 69.7-94.6% and Chapter 3 from 66.8-81.6%. Participants obtained an optimal learning experience in developing CAR proposals, among them were to identify problems, to develop methodologies and comprehensiveness of the proposal, to diagnose the difficulties in developing proposals and to obtain valuable input for the improvement of their research proposals.