Add milk, yogurt, 1 cup blueberries, and 1 banana to a high-powered blender. Pulse a few times to help break down the fruit.
Add 3/4 cup oats and 1 teaspoon of lemon zest to the blender; mix well, adding ice if desired until the preferred consistency is reached.
Slice the remaining banana.
Divide the smoothie equally among 4 bowls. Top each serving with some sliced bananas, blueberries, oats and coconut flakes. Garnish with a lemon slice if desired.