In a large mixing bowl, combine the pancake mix, milk, egg, oil, and cinnamon. Stir gently until just combined, leaving the batter slightly lumpy. Carefully fold in the blueberries.
Pour the batter into a greased 15x10x1-inch baking pan, spreading it evenly. Bake in a preheated oven at 400°F for 10-12 minutes, or until the top is golden brown and a toothpick inserted comes out clean.
Once baked, slice into squares or triangles. Serve with a generous amount of butter and a drizzle of maple syrup. Reheat in the microwave for a convenient breakfast option.