Preheat the oven to 375°F (190°C).
In an 8-inch (20 cm) square (or similar-sized) baking dish, mix together the oats, lentils, baking powder, cinnamon, and salt. Scatter with berries and coconut.
In another bowl, whisk together the milk, maple syrup, egg, butter, and vanilla. Pour the mixture over the oats, and give it a gentle stir to distribute everything evenly.
Bake for 40 minutes, or until the top is golden and the oats have set. Serve warm, topped with milk or a splash of cream. Leftovers reheat beautifully.
