Preheat oven to 350F and grease a 9-inch square baking dish with butter or oil.
Combine the dry ingredients in a large mixing bowl: oats, baking powder, cinnamon, and salt.
In a medium-size bowl, whisk the milk, eggs, vanilla extract, and sweetener of choice (honey or maple syrup).
Add the wet ingredients to dry ingredients and stir to combine. Finally, stir in the melted coconut oil (or butter). You don’t want to stir the coconut oil into the milk or you will have clumps--that's why we're adding it after the ingredients are mixed.
Let the oatmeal rest for 5 minutes for the oats to absorb the liquids.
Gently fold the frozen blueberries into the oatmeal and pour into the prepared baking pan. Smooth out the top of the oatmeal with your spoon or the back of a measuring cup.
Bake for 30-35 minutes, until the center is firm and edges are browned.
Let rest for 5 minutes before serving.
*The amount of sweetener used will depend on your personal taste. For a sweeter oatmeal (although not overly sweet), I love 1/2 cup. If you want a oatmeal that's not sweet, 1/3 cup may work better for you. **While this recipe was tested and written as a baked blueberry oatmeal, the seasonal possibilities are endless. You could use chopped apples or banana slices, or try nuts or seeds, or maybe peaches. I think it will be fun to experiment with this recipe throughout the year. Egg-Free Option: If you want to make this an egg-free recipe, use flax eggs. I like 2 tablespoons of ground flax + 5 tablespoons of warm water, let sit for 5 minutes. You will still want to follow the instructions above--after letting the flax sit to gel, it should be whisked into the milk.