Wash all produce. Remove the stems from the strawberries and blueberries (if any).
Peel banana and break into a few pieces. Add to the blender.
Add blackberries, blueberries and strawberries to the blender. Cover with oat milk.
Blend until smooth. Add ice cubes and blend again until smooth. Serve and enjoy immediately.
Leftover smoothie can be frozen into ice cube trays and added to future smoothies.
Notes
Fresh or frozen berries can be used. Let frozen fruit thaw for about 10 minutes before blending it up.If you are using fresh fruit, add a cup of ice cubes to the blender to keep your smoothie cold and to add some thickness. (Not needed if using frozen fruit.) If your smoothie is too thin: Add something to thicken it. A banana, Greek yogurt, chia seeds, oats and avocado can all help to add more texture to the smoothie.If your smoothie is too thick: An easy way to lighten it up is to add more liquid, such as orange juice or milk.