Combine the rolled oats, milk, yogurt, chia seeds, maple syrup or stevia, fresh berries, and, if desired, cinnamon and vanilla in a jar or storage container with a lid.
Mix all ingredients thoroughly. Secure the lid and refrigerate the mixture overnight.
In the morning or when ready to consume, remove the lid and stir the oats. If the consistency is too thick, add a small amount of milk to reach your preferred texture.
Garnish with additional fresh berries and enjoy. These oats can be eaten directly from the jar or transferred to a bowl for serving.