The present study investigated the extent to which monitoring practice and timely monitoring feedback, contextualized in an online undergraduate biology course, improved students' metacognitive monitoring and learning outcomes. The intervention followed a true experimental design and randomly assigned 162 students into three conditions: a control condition, a monitoring practice (MP) condition, and a monitoring practice and timely monitoring feedback (MP + MF) condition. Students in the control condition received weekly content practice in alignment with the concurrent course content. Students in the MP condition also received weekly content practice but in addition received monitoring practice for each weekly practice session. In the MP + MF condition, students additionally received timely monitoring feedback for each item, which indicated whether they were underconfident, accurate, or overconfident in their answers. Results showed that students across the three conditions reported higher metacognitive awareness and self-efficacy for strategic learning. Additionally, students in the MP + MF condition were more accurate in monitoring their learning, especially in monitoring the difficult knowledge items when compared to the control condition. Students' qualitative judgment justification responses also demonstrated the factors they considered when judging their performance. Implications for future research and practice are discussed.