In an almost-empty peanut butter jar or another resealable glass jar, combine all ingredients except banana and apples.
Seal jar and refrigerate overnight.
Top with banana slices and diced apple in the morning.
Serve cold, room temp or pop in the microwave for 30 seconds to warm. Steel cuts will have a nice chew to them but if you prefer to cook them further, add 1/4 c extra milk and microwave for 90 seconds.