In higher education, formative academic literacy assessment tends to prioritise the product, i.e. a written text, rather than the writing processes, i.e. an active and focused reading which leads to the development of an evidence-based argument. This paper shifts the emphasis from the written product to the writing processes and investigates the effectiveness of formative academic literacy assessment in facilitating students' engagement with composing processes and in helping them develop evidence-based writing. The study was conducted on a presessional programme, involved 15 students and used an online learning platform to stimulate students' criticality, evidence their active reading, and compile their formative essay in incremental steps of note-taking, outlining and paragraphing. Collected data (outlines/essays with feedback, student-generated digital artefacts, and questionnaires/follow-up interviews) were analysed qualitatively, employing genre/inductive analysis for student writing, semiotic analysis for students' digital sites, and thematic analysis for questionnaires/interviews. The findings indicate that emphasising composing processes and utilising an online platform to scaffold formative academic literacy assessment boosts students' understanding of text composition and helps to uncover and overcome difficulties encountered by student-writers while learning to write. The discussion highlights the educational value of online learning platforms and the affordances of multimodal resources in creating innovative assessment practices.