Peel the banana and break it in half. Rinse and pat dry your apple. Cut the apple into wedges using a paring knife or an apple corer/slicer.
If you don't have a Vitamix, start by placing the oats in your blender and pulsing them a few times to break them up.
Place all ingredients in the blender. Blend until smooth and you can't detect the oat texture. (If you have a Vitamix, you can insert the tamper through the lid to push the fruit into the blades while blending.)
If using a frozen banana, just add five small ice cubes or a couple large ones.
I use raw, rolled oats in this recipe. Plain, quick-cooking oats also should work. Don't use steel-cut oats here, because they won't blend as well.
This makes enough for two glasses, but I usually drink the whole thing. The calories listed are for the full batch, but if you only drink half, it has 266 calories.