Preheat your oven to 375°F (190°C) and lightly grease a small oven-safe baking dish or large ramekin with a touch of coconut oil.
In a medium mixing bowl, whisk together the Greek yogurt, liquid egg whites, vanilla extract, and maple syrup until the mixture is smooth and well combined.
Add the rolled oats, chia seeds, cinnamon, baking powder, and sea salt to the wet ingredients, stirring until the oats are fully submerged and the spices are evenly distributed.
Gently fold in half of the mixed berries, being careful not to over-mix so the batter doesn't turn entirely purple.
Pour the oatmeal mixture into the prepared baking dish and spread it into an even layer.
Scatter the remaining berries over the top, pressing them slightly into the surface for a beautiful presentation.
Bake for 25 to 30 minutes, or until the center is set and the edges are lightly golden and pulling away from the sides.
Remove from the oven and let it cool for 5 minutes to allow the texture to firm up before serving warm.