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 smooth and fully incorporated.
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 blueberries into the batter, distributing them evenly throughout.
05 - Pour batter into prepared baking dish and smooth the top with a spatula. If using, sprinkle sliced almonds and chia seeds evenly over surface.
06 - Bake for 35 minutes or until center is firm and top is golden brown. A toothpick inserted in center should come out clean.
07 - Let cool for 5 to 10 minutes before slicing into squares. Serve warm or at room temperature.