The notion of grammatical metaphor (GM) (Halliday, 1985) is essentially where a writer can shift an action or quality into being a ‘thing’. As in most senses of metaphor, the goal is to “represent something as something else” (McGrath & Liardét, 2023, p.33). This study investigated the use of grammatical metaphor (GM) in Linguaskill writing exam responses across CEFR proficiency levels (below-B1 to C1 or above). It analysed the presence of a pre-existing GM list (see McGrath & Liardét, 2023) to explore GM frequency in L2 responses, the correlative relationship with proficiency scores and qualitatively explored candidate responses in terms of how GMs were used. Results show a moderate positive correlation between proficiency and GM use, with a dominance of process-to-thing shifts (e.g., transform→transformation) and emergence of GM use from lower to higher proficiency levels. This underscores GM's significance in crafting academically valued meanings in L2 contexts, suggesting its potential for informing instructional and assessment practices. • Metaphorisation in Writing is a useful metric for L2 writing assessment. • Evidence suggests GM frequency correlates with increased performance. • Learners progress from emergent arguments to presenting ideas more concisely. • The majority of GM shifts were to ‘things’. • The study provides further weight to arguments for meaning-based complexity.