Preheat oven to 200°C (400°F).
Cut acorn squash in half and remove seeds.
Brush with oil, season with salt and pepper, and roast cut-side down for 25–30 minutes.
Heat oil in a pan and sauté onions and garlic until soft.
Add cooked grains (like quinoa or rice), vegetables, and spices; mix well.
Flip roasted squash and fill with the prepared stuffing.
Return to oven and bake for another 10–15 minutes.
Garnish with fresh herbs and serve warm.