Findings around the cognitive resources needed to compose text have helped shape current models of writing. Some of these models predict that text generation is constrained by two groups of skills: transcription (i.e., spelling and handwriting) and executive functions (EFs). While the constraining role of transcription on text generation is robust, the relationship between writing and EFs is more scarce. Some studies suggest that the impact of EFs on writing development is not only direct, but also indirect, through transcription skills. However, few studies have analyzed these effects over a sufficiently wide developmental period. In this paper, we examined transcription and EF skills in a large sample of beginner (G2), intermediate (G4), and upper-intermediate (G8) children (N = 1337). Each participant produced a narrative and an opinion essay. In addition, we collected measures of the low-level EFs of inhibition and updating of working memory, as well as measures of handwriting fluency and spelling accuracy. Results showed that EFs impacted text generation directly and indirectly via transcription skills, especially via handwriting. Transcription skills constrained text generation across grade levels and its weight was similar from the youngest through to the oldest age group. We conclude that EFs support low-level writing skills, as well as key processes involved in children's text composing (i.e., knowledge-telling processes). Relevant educational implications are discussed.