Reading for writing tasks have been widely implemented in past decades, but research is still scarce on computer-mediated reading for writing. With a growing interest in collaborative writing and collaborative reading, spurred on by the broader awareness of sociocultural theory and the collaborative nature of digital technologies, we proposed an innovative task "collaborative reading for writing" (CRW) and implemented it with graduate students of diverse L1s in the U.S. The students jointly read and annotated journal articles "via" the social annotation tool Perusall and then co-constructed OASIS summaries based on the reading. This study examines how the students employ comprehension strategies during collaborative reading/annotating; how they develop genre knowledge and attend to form during collaborative writing; and how they perceive CRW tasks. Data collected included the Perusall annotations, recorded pair talk, and reflection papers. Results showed that online CRW positively impacted learning by engaging learners in collectively expanding their reading strategies and enhancing genre knowledge and attention to form. CRW afforded mutual scaffolding and reading for a purpose. We posit that CRW tasks can have immense potential in diverse academic learning contexts where L2 writers are present. Future research is desired to examine the long-term effects of CRW on the development of L2 literacy skills and explore the potential of CRW tasks among different learner populations in other educational settings.