This study demonstrates learners’ learning paths in their extensive reading (ER) progress using two types of scaffolding for comprehension monitoring: quiz taking and discussion. Although the importance of socially constructed meaning is emphasized in critical literature (Gee, 2003), such a reading comprehension perspective has been investigated less in L2 ER literature. To promote outside-of-class ER using online materials in the Japanese high school context, the effects of two different types of self-selected scaffolding regarding spontaneous reading were examined, i.e., online comprehension quizzes and a cyber classroom where learners discuss books they had read. The results of the mixed methods —semi-structured survey and target students’ interviews —revealed that the quizzes could give learners with less confidence in L2 an explicit scale of their cognitive competence; however, the collaborative practice was more promising for establishing their reading habits and enhancing self-efficacy as they realized their identities as community members.