Preheat the oven to 375°F. Grease an 8x8 baking dish or a 9-inch pie dish with butter or cooking oil spray.
In a mixing bowl, combine the oats, almonds, chia and flax seeds, erythritol, cinnamon, baking powder, and salt.
In a separate bowl, whisk together the egg, melted butter, and almond milk.
Pour the liquid mixture over the oat mixture. Stir to combine.
Arrange about 2/3 of the berries and chopped apples on the bottom of the prepared dish. Pour the oatmeal mixture over the top.
Sprinkle the remaining 1/3 berries with apples on top.
Place in the oven and bake for 35 -40 minutes, until the oatmeal is set in the middle.
Serve with more fresh berries, if desired, and enjoy!