Scholars have described numerous accumulated purposes for reading in composition courses, but students’ reading practices remain largely invisible to instructors. Recent developments in social annotation tools allow readers to share the margins of digital texts, transforming reading from a private to a public activity. These tools make visible the reading practices of students, several or a whole-class at a time, and at multiple points in the term. Based a study of social annotation in first-year composition, results indicate that students, rather than approaching texts with a single purpose, shift among and layer reading lenses focused on ideas, rhetoric, ideology, and affect. The purposes for and ways of reading made visible in this study inform the design of reading instruction in the composition course to develop students’ reading strategies to improve their writing development.