Preheat your oven to 350 degrees Fahrenheit. Spray a 9 by 13 inch baking dish with cooking spray and set aside.
In a large bowl mix together the oats, brown sugar, ground cinnamon, baking powder, and salt.
3 cups old fashioned oats, 1/2 cup brown sugar, 2 teaspoons ground cinnamon, 2 teaspoons baking powder, 1 teaspoon table salt
Stir in the eggs, milk, butter, honey, and vanilla. Then stir in the blueberries and pecans (if using).
3 large eggs, 2 cups milk, 1/2 cup melted butter, 2 teaspoons vanilla extract, 2 cups fresh or frozen blueberries, 1/2 cup chopped pecans, 2 tablespoons honey
Pour into the prepared baking dish. Bake uncovered for 35 to 40 minutes, or until the top is golden and the middle is set but still has a slight jiggle. Remove from the oven and let it stand for 10 minutes before cutting and serving.