Grade 4 represents a critical juncture in the literacy development of young students. This article explores the role of handwriting in unlocking the higher order psycholinguistic and metacognitive resources needed to compose quality text. In particular, we investigate the threshold of control over handwriting needed to unlock vocabulary that contributes the greatest proportion of the variance in the quality of 245 students' writing samples. Using online vocabulary profiling tools we tap 2 measures of vocabulary use in addition to a standard vocabulary measure. Outcomes provide direction to classroom practitioners for focusing sustained instructional attention on handwriting in the Grade 4 year, ongoing vocabulary work, and metacognitive strategies in the writing process that have potential for ameliorating academic literacy outcomes.