Place four jars on a flat surface. Fill each jar with ½ cup old-fashioned oats, ¼ cup yogurt, ½ cup milk, and ½ teaspoon vanilla (if using). Stir to combine.
Want to add fruit? Add up to ½ cup berries or diced fruit per jar, depending on how much you can fit.
Chill
Refrigerate overnight, with a minimum of 4 hours. These can be prepped ahead and refrigerated for up to 3 days with fruit, up to 5 days without fruit. Personally, I prep them plain, then add fruit before serving.
Serve
When ready to eat, stir to combine. Enjoy cold, as is, or warmed in the microwave for 30 seconds to 1 minute.
Notes
Add-ins: make these more nutritious by adding ½ teaspoon chia seeds or 1 teaspoon flax meal per jar.