The predictive relationship between handwriting automaticity and children’s writing performance is well documented. However, less is known about the relationship between keyboarding automaticity and children’s keyboard-based writing performance. In this exploratory study, we examined the unique contributions of automaticity in both writing modalities in predicting Grade 2 students (N = 49) paper-based and keyboard-based writing performance (i.e., compositional quality and fluency) after controlling for students’ literacy skills (i.e., spelling, word reading, and reading comprehension), attitudes toward writing, gender, and nesting due to classroom. Multilevel modelling results showed that automaticity predicted students’ paper-based compositional quality and keyboard-based compositional quality and fluency. Findings further suggested that the relationship between automaticity and writing performance was stronger in keyboard-based text composing than in paper-based text composing. These results reinforce the role of automaticity of transcription skills in predicating the writing performance of beginning writers across modalities and stress the significance of explicit pedagogy and frequent instances of practice to promote the mastery of transcription skills across modalities in the early years of schooling.