Preheat oven to 350 degrees F. Grease a baking dish (8×8 or 7×10).
In a medium bowl, toss together blueberries, lemon zest and juice, maple syrup, and vanilla extract. Pour mixture into baking dish.
In another bowl, whisk together milk, ghee, maple syrup, egg, and vanilla extract. Then fold oats, baking powder, and salt. Pour mixture on top of blueberries and spread out evenly throughout dish.
Place in the oven to bake for 1 hour. Top with yogurt before serving!