This study investigated how quality of the classroom learning environment influenced first grade students' (n=533) time spent in two non-instructional classroom activities (off-task and in transition) and their subsequent literacy outcomes. Hierarchical linear modeling revealed that higher classroom quality was related to higher student performance in reading comprehension and expressive vocabulary. Further, classroom quality predicted the amount of time students spent off-task and in transitions in the classroom, with slopes of change across the year particularly impacted. Mediation effects were detected in the case of expressive vocabulary such that the influence of classroom quality on students' achievement operated through students' time spent in these non-instructional activities. Results highlight the importance of overall classroom quality to how students navigate the classroom environment during learning opportunities, with subsequent literacy achievement impacted. Implications for policy and educational practices are discussed.