The authors investigated the impact of explicit instruction and peer-assisted writing on students' writing motivation and self-efficacy for writing. Eleven teachers and their 206 fifth- and sixth-grade students participated in a 2 (explicit instruction vs. writing opportunities without explicit instruction) × 2 (peer-assisted writing vs. writing individually) experimental intervention study with a pretest-posttest design. The four experimental conditions were compared with a business-as-usual (BAU) condition. The five-week interventions were implemented in authentic classes by regular class teachers, who received a prior professional development training. Multilevel analyses showed that students who wrote with a peer were more autonomously motivated at posttest than BAU students. Additionally, BAU students and students receiving explicit instruction were more controlled motivated than students who were offered ample writing opportunities while practicing individually. Theoretical and educational implications are discussed in view of realizing a bright pathway towards autonomous writing motivation.