Heritage language (HL) bilinguals' writing skills has been a topic of inquiry in the field of HL education. However, little is still known about HL writers' writing processes and the contribution of individual differences to these processes remains unexplored. By integrating keystroke-logging and think-aloud methodologies, this study examined 61 Spanish-English HL writers' pausing and revision behaviors during the completion of Spanish (HL) and English writing tasks. Participants also completed an advanced Ospan working memory test and a language dominance questionnaire. The main findings revealed that, although HL writers' pausing and revision behaviors did not significantly differ between writing tasks, the nature of their writing processes underlying these writing behaviors fluctuated. Further, language dominance as a multidimensional construct did not contribute to these writing results, whereas participants with higher working memory spent more time addressing orthographic and morphosyntactic encoding episodes during pauses within words when writing in both languages.