Autistic children demonstrate highly variable written language skills. Existing research has focused on examining autistic children's performance on direct assessments of written language. In contrast, few studies have sought to understand how autistic children conceptualize their writing abilities or engage with writing across different contexts compared to non-autistic peers. This study used a researcher-designed questionnaire to examine writing self-concept, text engagement with different writing activities, and writing practices and beliefs across school and non-school contexts in school-age (10-18 years old) autistic children compared to their non-autistic peers. Data analysis approaches included "multiple indicators, multiple causes" (MIMIC) modeling; correlational and multiple regression analysis; non-parametric Mann-Whitney U tests; and principal components analysis. Groups did not differ in their writing self-concept ratings. Furthermore, both groups engaged with a variety of different writing activities to a similar extent except for text messages being lower for the autistic group. Five components were extracted via principal components analysis on items related to writing practices and beliefs across contexts; groups did not differ across the components. Overall, the non-autistic group showed more consistent relationships between writing self-concept as well as writing practices and beliefs with performance on a narrative writing task when compared to the autistic group. Results offer a preliminary understanding into how autistic children engage with writing across contexts for a variety of purposes when compared to their non-autistic peers and offer implications for continued research and educational practice.