Highlights: • Investigated history writing at an American university in the Middle East. • Examined how source text and prompts condition the genres that students produce. • Source texts and prompts had effects individually and in combination. Abstract: Argumentative writing is a vital but challenging genre for university students, particularly second language writers. While much is known about different factors that make it challenging, in this paper, we focus on an underexplored factor: the intertextual relationship between source texts, prompts, and student writing. We analyze student writing in a first-year history class at a branch campus of an American university in the Middle East, and more specifically, how source texts and writing prompts condition whether students produce the expected argument genre. We draw from two perspectives on genre: Rhetorical Genre Studies, with its focus on the highly contextualized nature of writing, provides a useful lens through which to view intertextuality; Systemic Functional Linguistics, with its explicit focus on language, provides tools for studying writing development in school genres. Results suggest that source texts that do not contain an explicit argument and prompts that ask for students’ opinion may facilitate students’ uptake of argument. The study has pedagogical implications for improving alignment between an instructor's goals and expectations, assignment design, and the writing students produce.