01 - Preheat oven to 350°F (175°C). Lightly grease an 8x8-inch (20x20 cm) baking dish with cooking spray or a small amount of oil.
02 - In a large mixing bowl, whisk together Greek yogurt, eggs, almond milk, maple syrup, lemon juice, lemon zest, and vanilla extract until completely smooth and well incorporated.
03 - Add rolled oats, protein powder, baking powder, and salt to the wet mixture. Stir until just combined, being careful not to overmix.
04 - Gently fold in the blueberries using a spatula, distributing them evenly throughout the batter.
05 - Pour the mixture into the prepared baking dish and smooth the top with a spatula. If desired, evenly sprinkle sliced almonds and chia seeds over the surface.
06 - Bake for 35 minutes, or until the center is set and the top is golden brown. A toothpick inserted into the center should come out mostly clean.
07 - Allow the breakfast bake to cool for 5-10 minutes before slicing into squares. Serve warm or at room temperature.