Preheat your air fryer to 350°F (175°C) for 5 minutes.
In a large bowl, whisk together the milk, beaten egg, maple syrup, vanilla extract, baking powder, cinnamon, and salt until smooth.
Stir in the rolled oats until fully coated in the liquid mixture.
Gently fold in about 1.5 cups of the mixed berries, reserving the rest for topping.
Pour the oatmeal batter into a greased 7-inch round cake pan that fits inside your air fryer basket.
Place the pan in the air fryer basket and cook at 350°F for 18-22 minutes, or until the top is golden and the center is set.
Carefully remove the pan from the air fryer. Let it cool for 5 minutes, then top with the remaining fresh berries and a drizzle of maple syrup.
Serve warm directly from the pan or slice into wedges for a beautiful brunch presentation.