Preheat the oven to 375°F and spray an 8x10 inch baking dish with cooking spray.
Line it with parchment paper to make things to clean afterward.
In a large mixing bowl, combine oats, baking powder, Cinnamon (if using), lemon zest, and salt.
In another bowl whisk eggs, milk, maple syrup or honey, lemon juice, oil, and vanilla extract.
Next, pour the liquid mixture into the oats. Gently fold to fully combine.
Stir in 3/4 cup of the blueberries and fold again.
Now pour the mixture into the prepared baking dish, using a spatula or the back of a spoon, hard-pack the mixture to create an even smooth top. Add the rest of the blueberrues on top.
Bake for 25-30 minutes or until the topping smells toasty and looks golden brown.
Place the pan on a wire rack to cool completely.
Divide into 6 squares, garnish with the remaining fresh berries on top, and serve with plain yogurt.