Measure out the rolled oats and pour them into a clean jar or container with a lid.
Add the milk, vanilla bean paste, and sweetener to the jar with oats.
Secure the lid on the jar and shake vigorously until the mixture is well combined and the oats are evenly coated.
Place the jar in the refrigerator and let it soak for at least 2 hours, or preferably overnight, allowing the oats to absorb the liquid and soften.
Remove the jar from the fridge and stir the oats to redistribute the soaked mixture. Observe the creamy, pudding-like texture with visible vanilla flecks.
Serve the overnight oats directly from the jar or transfer into a bowl, garnishing with fresh fruit, nuts, or additional sweetener, if desired.