Preheat oven to 375°F and grease a 9 x 13" baking dish.
In a large bowl, mix together the oats, brown sugar, baking powder, cinnamon and salt. Add in half of the strawberries, half of the blueberries and half of the chocolate chips. Mix well.
In a separate bowl whisk together the eggs, milk, coconut oil and vanilla extract.
Distribute the oat mixture evenly in the baking dish and then pour the wet ingredients over the dry mixture. Make sure the oats are covered in the wet ingredients.
Add the remaining berries, chocolate chips and the sliced banana to the top of the casserole.
Bake for 35-40 minutes. Allow the casserole to cool for 5 minutes before serving. Top with yogurt or maple syrup and enjoy!