This paper explores cross-cultural and grade-based differences in the use of intertextual resources in persuasive essays written by tertiary students. Expressions of explicit intertextuality are analysed using the model of Attribution, an element of the engagement system formulated within the interpersonal metafunction of Systemic Functional Linguistics. The text analysis, supported by interview results, reveals that while there are some differences in the overall use of Attribution between native English speaking and ESL students, the most significant grade-based differences were found in expressions of Attribution and in the Attribution patterns adopted in the presentation of intersubjective claims supported by evidence. The differences identified are interpreted in terms of dialogic literacy perspectives. Pedagogical implications are discussed in terms of the contribution of the differences to the success of the essays, and the need to support academic literacy.