Previous research has shown that speech-to-text (STT) software can support students in producing a given piece of writing. This is the 1st study to investigate the use of STT to teach a writing strategy. We pretested 45 Grade 5 students on argument writing and trained them to use STT. Students participated in 4 lessons on an argument writing strategy and wrote a practice text for each lesson. We then randomly assigned the students to compose practice texts in 1 of 2 modalities: handwriting or STT. Students then completed posttests on argument writing in both modalities. Both modality conditions resulted in statistically significant, large gains in text quality, word count, and variety of argument moves and significant transfer to the untrained modality. The modalities did not differ significantly in their effects on argument writing or cognitive load. The results suggest that STT provides an alternative medium for learning writing strategies.