01 - Preheat oven to 350°F. Lightly grease an 8x8-inch baking dish with cooking spray or butter.
02 - In a large mixing bowl, whisk Greek yogurt, eggs, almond milk, maple syrup, lemon juice, lemon zest, and vanilla extract until completely smooth and well combined.
03 - Add rolled oats, protein powder, baking powder, and salt to the wet mixture. Stir gently until just combined, being careful not to overmix.
04 - Gently fold in the blueberries, distributing them evenly throughout the batter.
05 - Pour the mixture into the prepared baking dish and smooth the top with a spatula. Sprinkle sliced almonds and chia seeds evenly over the surface if using.
06 - Bake for 35 minutes until the center is set and firm to the touch, and the top is golden brown.
07 - Let the breakfast bake cool for 5 to 10 minutes before slicing into squares. Serve warm or at room temperature.