The argumentative essay has endured as a popular form of university assessment, yet students still struggle to meet key intended learning outcomes, such as those associated with critical thinking. This paper presents the results of a study that examines the instruction provided by Australian essay writing guides to support students' development of a questioning, critical viewpoint. Thirty publically available guides were chosen from a range of university types, and sourced from central student learning units and humanities disciplines. Findings of this documentary analysis show that some guides provide too little context for essay writing as an academic practice, and conceptualise definitional, instructional and procedural aspects of the task in ways that may not align with intended outcomes. The conclusion indicates a need for further research about the teaching of argumentative essay writing.