To make this Scottish Potato & Cabbage Casserole gluten-free, ensure that your cheddar cheese is certified gluten-free, as some pre-shredded varieties may contain anti-caking agents derived from gluten. Additionally, check the butter and seasonings for hidden gluten additives (rare, but worth confirming). The recipe itself is naturally free of flour or bread-based ingredients, making it an excellent gluten-free option with minimal adjustments.