Preheat oven to 350 degrees. Spray an 8x8-inch baking dish with cooking spray.
In a large mixing bowl, combine oats, brown sugar, baking powder, salt, and cinnamon. Stir with a wire whisk to break up clumps.
In a separate smaller bowl, add the lightly beaten eggs (I crack the eggs into the small bowl and just use a fork to mix), milk, and melted butter. Stir with a whisk.
Add the milk mixture to the oatmeal and stir together until everything is combined. Add the fruit and gently mix together.
Spread the oatmeal batter into the prepared dish. Top with additional chopped peaches and blueberries, if wanted.
Bake for 35-40 minutes. Edges will be golden brown and the middle should look set but still slightly jiggly. Let it cook for about 15 minutes and then cut into squares.
Serve with a drizzle of milk, or put milk in the bottom of the bowl, and additional chopped fruit to garnish.