Research on expert performance suggests that deliberate practice provides optimal opportunities for expertise development. This study examined whether the provision of computer-based scaffolding (CBS) guiding deliberate practice facilitates students' development of writing expertise. A CBS environment "escribo" was designed to externally support expert writing activities, generate feedback and offer opportunities to practise corrected performance in academic writing. There were two testing times. First, the effects of practising writing with "escribo" were compared with the effects of a practice-only situation without support. Second, a post-test comprised composing an essay discussing an academic position without scaffolding. Results revealed that the "escribo" group at both testing times wrote essays of better comprehensibility than students in the practice-only group. Furthermore, at both testing times the "escribo" group expended significantly more time on prewriting. These findings suggest that CBS guiding deliberate practice may be a promising means to facilitate the development of writing expertise. (Contains 2 figures and 4 tables.)