Educational theorists have argued that effective instruction in quantitative reasoning (QR) should extend across the curriculum. While a noble goal, it is not immediately evident that this is even possible. To assess the feasibility of this approach to QR instruction, I examine papers written by undergraduates for submission to a sophomore writing portfolio. I distinguish papers in which QR is central to the main thrust of the argument ("centrally relevant") from those in which QR would strengthen the argument by providing context, enriching description, or presenting background ("peripherally relevant"). I find extensive potential for QR instruction across the curriculum. In 25% of papers QR was centrally relevant and in another roughly 20% QR was peripherally so. Of papers for which QR is centrally (peripherally) relevant, around 50% (95%) were written outside natural science courses. Moreover, 30% of papers written in arts, literature, and humanities courses were QR relevant.