01 - Preheat oven to 350°F. Lightly grease an 8x8-inch baking dish with cooking spray or a small amount of oil.
02 - In a large mixing bowl, whisk Greek yogurt, eggs, almond milk, maple syrup, lemon juice, lemon zest, and vanilla extract until smooth and fully combined.
03 - Add oats, protein powder, baking powder, and salt to the wet mixture. Stir until just combined, being careful not to overmix.
04 - Gently fold blueberries into the batter using a spatula, taking care not to crush the berries.
05 - Pour 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, or until the center is set and the top is golden brown. A toothpick inserted in the center should come out clean.
07 - Let cool for 5 to 10 minutes before slicing into squares. Serve warm or at room temperature.