Writing is an important activity that involves many demanding processes. Given the complexity and goal-directed nature of writing, this activity is heavily dependent on executive functions (EFs). This study aimed to examine the longitudinal contribution of EFs (i.e., inhibitory control, working memory, cognitive flexibility, and planning) to text quality in Grade 2. One hundred and sixteen Portuguese native speakers in Grade 2 (M[subscript age] = 7.26 years; SD = 0.29) participated in two measurement occasions with a 6-month interval (viz., Fall and Spring). In the Fall measurement, students completed EFs and writing tasks, while in the Spring measurement, students completed writing tasks only. We conducted a set of hierarchical regression analyses to examine the contribution of EFs measured in the Fall to story quality measured both in the Fall and in the Spring. Results showed that working memory and planning at the beginning of the school year had a significant and unique contribution to text quality 6 months later, above and beyond the effects of gender, reasoning, and transcription skills. These findings provide evidence of the key role of working memory and planning in children's writing. From an applied side, this study also indicates that teachers should aim to promote EFs in order to support writing in young learners.