Task-based research has investigated the learning opportunities (e.g. language related episodes) that emerge during heritage and second language learner interactions during writing tasks. However, to date, it is unknown how these peer interactions involving heritage language learners contribute to written texts. Further, given the rise of social technologies in educational settings, a need exists to examine how interactions in digital platforms affect the production of written texts. To address these issues, 13 heritage-second language learner and 16 heritage–heritage learner pairs enrolled in advanced Spanish content courses completed two distinct versions of writing tasks. Participants were instructed that they were hired as business consultants for clothing and cellphone companies in Spain. While each participant wrote her or his own version, the pairs had to interact to compose formal business letters in Spanish to the CEO of each company justifying the hiring (Task A) or laying off (Task B) of employees. The main results first revealed that heritage–heritage pairs produced more syntactically complex business letters, as evidenced by a greater ratio of syntactic subordination along with a minor trend of greater morphosyntactic accuracy. Second, synchronous computer-mediated communication interactions led to a higher production of syntactic coordination, especially for the heritage-second language pairs. Findings are discussed in light of the interplay between learner factors and task environment.