In a medium mixing bowl, add rolled oats and milk. Stir gently until oats are fully submerged and let mixture rest for a minute.

Add maple syrup, brown sugar, cinnamon, and vanilla extract. Stir well until sweeteners are dissolved and spices are evenly distributed.

Divide the oat mixture into airtight serving containers. Seal and refrigerate for at least 6 hours or overnight.

Preheat oven to 350°F. Spread nuts on a baking sheet and bake for 7-10 minutes until golden and fragrant.

Sprinkle toasted nuts over the overnight oats before serving. Add Greek yogurt if desired.