Combine the oats, vanilla, probiotic powder, chia seeds, almond milk, cinnamon and salt into a Mason jar or bowl that can be sealed. Stir well to combine.
Seal and refrigerate overnight or for at least 4 hours. When ready to eat, top with diced peaches and chopped walnuts. If oats seem a bit dry in the morning, add a tablespoon or two of additional milk and stir in. If using frozen peaches, let thaw in the jar with the oatmeal overnight.