Despite teachers' mainstream practices in L2 writing classrooms addressing different dimensions of writing over time, much of the research on feedback in recent years has been of relative short duration and has mainly focused on accuracy. The current longitudinal study investigated the influence of sustained teacher written feedback on accuracy, syntactic complexity, fluency, content, and organization in an EFL context. Ninety-two learners were divided into four groups, receiving written corrective feedback, feedback on content and organization, multilateral feedback (i.e., on grammatical accuracy, content, and organization), and no feedback over a 3½-month period. They completed a pre-test, post-test, and delayed post-test and wrote and revised eight interim expository compositions on a weekly basis. Results showed that the three treatment groups significantly improved in the dimensions on which they received feedback. However, only the groups who received feedback on content and organization improved in fluency. Importantly, the multilateral group improved in accuracy as well as fluency, content and organization. Theoretically, the findings endorse the language learning potentials of sustained writing as long as it is guided by teacher feedback. The findings provide empirical support for the influence of sustained feedback on expanding and consolidating learners' explicit knowledge of L2 writing.