Preheat oven to 350 degrees Fahrenheit and spray an 8"x8" glass baking dish with cooking spray.
In a large mixing bowl, combine the flax seed and water and stir well. Let it sit for 5 minutes or until it starts to thicken.
Add the rest of the liquid ingredients (coconut milk, maple syrup, lemon juice, and zest, blueberries) to the bowl with the flax and whisk to combine.
In a second bowl, combine the dry ingredients (oats, baking powder, and salt) and stir together to combine.
Add the dry ingredients to the wet ingredients and stir well. Stir in the blueberries.
Bake for 40-45 minutes or until top of the oatmeal is golden brown and the middle no longer jiggles when you give the pan a shake.
Allow to cool on the counter a few minutes before cutting into pieces to serve.