Add rolled oats, milk, Greek yogurt, maple syrup, chia seeds, vanilla extract, and sea salt to a mason jar or airtight container.
Stir thoroughly until all ingredients are well combined.
Cover with a lid and refrigerate overnight.
If you're short on time, allow the oats to soak for at least 2 to 4 hours.
When ready to serve, remove from the refrigerator and stir well.
Add a splash of milk if the mixture is thicker than desired.
Top with your favorite toppings and enjoy directly from the jar or transfer to a serving bowl.