The purpose of this study is to examine whether written competence gained from CMC based written communication could be transferred to students' oral proficiency and could promote positive attitude. To test the research hypothesis, the effects of three different types of written practice were studied. In this study, it was found that the experimental group who conducted CMC based written communication outperformed other groups in oral proficiency and attitude. These findings support the idea that CMC components provide circumstances of facilitating interactions between student and student. Since CMC based written communication is asynchronous, it allows for a moderation of ideas, phrasing, and rephrasing of ideas before expressing them. Thus, more writing practice resulting from using CMC components is believed to foster students' oral proficiency, expecially in the areas of vocabulary selection, fluency, and logical development.