The benefits of writing strategy feedback are well established. This study examined the extent to which adding spelling and grammar checkers support writing and revision in comparison to providing writing strategy feedback alone. High school students (n = 119) wrote and revised six persuasive essays in Writing Pal, an automated writing evaluation and tutoring system. All participants received automated strategy feedback after writing the first draft of their essays. Half of the participants were also given access to spelling and grammar checkers while writing. Spelling and grammar feedback on its own had no effect on the quality of students' first draft. Linear mixed effects models revealed improvements from initial draft to revision on most subscales. The addition of spelling and grammar feedback contributed small but significant gains after revision on five subscales (i.e., mechanics, word choice, voice, conclusion, and organization) but no other aspects of the students' essays. Qualitative exploration of exemplar students' revision moves revealed how students incorporated both strategy and spelling and grammar feedback into their revisions. Findings from this study demonstrate that strategy feedback with an opportunity to revise contributed to improved essay quality, but that spelling and grammar feedback provided modest, complementary benefits.