As an internal process, documenting reading comprehension has remained challenging. This paper presents three case studies that explore the transactional practices of literacy education graduate students as they read and annotate assigned texts in an online, asynchronous class. Social annotation tools give multiple students simultaneous access to the same text and allow them to interact with one another, which positions literacy as a social practice. Findings illuminate the different approaches participants engaged in to interact with the text and their peers, with regard to comprehension strategies, critique, and community interaction. Implications offer insight for teacher educators on assessing teacher reading comprehension through social annotation.