Autonomous learners are described as those who assume responsibility for and take charge of their own learning. However, research has pointed out that autonomy does not represent a fixed state but a developmental continuum, making it difficult to measure those in the transition of becoming autonomous. As one’s autonomy development can be explained by one’s self-regulatory behaviors, a learner’s development of autonomy can be investigated through how he/she evaluates his/her participation in a learning task. This study aimed to explore students’ self-regulation levels in the participation of writing assignments and revisions and their task engagement during the multi-drafting revision process. Twenty-eight students participated in this study. In an 18-week semester, the students were required to complete four writing projects, each with three drafts. The students received teacher feedback for revising their works. Data collection tools included one survey, students’ drafts, and one interview. The survey assessed the students’ learning attitudes/beliefs and their behavioral regulation; the writing drafts were used to identify their task engagement in revising from the first to the final drafts; the interview was further conducted to investigate factors affecting the students’ development of self-regulatory behaviors and task engagement. The findings showed that more than 90% of the students perceived writing as a good way to improve their analytical skills, master the English language, gain a sense of pride in their own ability, and enhance their future career. In addition, among the 28 students, 18 students demonstrated consistency between their Relative Autonomous Indexes (RAIs) and their task engagement levels. Another ten students were further interviewed, and their responses indicated that semester workload, extracurricular activities, and genre preference could impact one’s task engagement level in the revision process.