Combine Ingredients: In a mason jar or bowl, mix the rolled oats, milk, Greek yogurt, diced apple, cinnamon, honey or maple syrup, and a pinch of salt.
Stir Well: Ensure everything is well combined, then add chopped nuts if desired.
Refrigerate: Cover and refrigerate overnight (or for at least 4 hours) to let the oats soak and soften.
Serve: In the morning, give it a good stir and enjoy as is, or top with additional diced apples and a sprinkle of cinnamon.
