This study investigated the effect of incorporating spelling and grammar checking tools within an automated writing tutoring system, Writing Pal. High school students (n = 119) wrote and revised six persuasive essays. After initial drafts, all students received formative feedback about writing strategies. Half of the participants were also given access to spelling and grammar checking tools during the writing and revision periods. Linear mixed effects models revealed that essay quality for students in both conditions improved from initial draft to revision in terms of all aspects except essay unity. The availability of spelling and grammar checking yielded added improvements from initial draft to revision for several aspects of essay quality (i.e., conclusion, organization, voice, grammar/mechanics, and word choice), but other aspects were unaffected (i.e., introduction, body, unity, and sentence structure). The availability of spelling and grammar checking tools had no effect on holistic essay scores. These results indicate that automated spelling and grammar feedback contribute to modest, incremental improvements in writing quality that may complement automated strategy feedback. [This paper was published in: S. Isotani et al. (Eds.), "AIED 2019" (pp. 270-282). Switzerland: Springer.]