Preheat your oven to 350°F (175°C) and lightly grease a small baking dish with a touch of coconut oil.
In a medium mixing bowl, whisk together the rolled oats, vanilla pea protein powder, chia seeds, baking powder, ground cinnamon, and sea salt until well combined.
In a separate bowl, combine the egg whites, unsweetened almond milk, and vanilla extract, whisking until the mixture is slightly frothy.
Pour the wet ingredients into the dry ingredients and stir until just combined, then gently fold in the fresh or frozen mixed berries.
Transfer the mixture into the prepared baking dish, smoothing the top with a spatula to ensure the berries are evenly distributed.
Bake for 25 to 30 minutes, or until the center is set and the edges are golden brown and slightly pulled away from the sides.
Allow the oatmeal to cool for 5 minutes before slicing into squares and serving warm.