Metacognition directly contributes to learning, performance, and beliefs about the self as a learner. This paper describes the rationale, implementation, and assessment of a weekly online reflection activity based on instructor prompts designed for post-secondary students who aspire to be elementary school teachers. Our study defines four categories of metacognitive knowledge that speak to the specific goals of the course and the characteristics of the students. Using these categories, 71 students' written responses to four reflection prompts from three course offerings were coded, and their effects were examined in terms of types of metacognitive knowledge demonstrated. Our results not only confirm that students were engaged in metacognition through the reflection activity but also show that students exhibited different categories of metacognitive knowledge in relation to the varying emphases of the prompts.