01 - Preheat oven to 350°F. Grease an 8×8-inch baking dish with butter or nonstick spray.
02 - In a large mixing bowl, stir together the rolled oats, ground cinnamon, ground nutmeg, baking powder, and salt until evenly distributed.
03 - In a separate bowl, whisk together the eggs, milk, maple syrup (or honey), and vanilla extract until smooth and well blended.
04 - Pour the wet ingredient mixture into the dry ingredients and stir gently until just combined, being careful not to overmix.
05 - Gently fold in the grated carrots, chopped nuts, raisins, and shredded coconut (if using) until evenly distributed throughout the batter.
06 - Pour the oatmeal mixture into the prepared baking dish, using a spatula to spread it into an even layer.
07 - Bake for 35 to 40 minutes, or until the center is set and the top is lightly golden brown. A toothpick inserted in the middle should come out clean.
08 - Allow the baked oatmeal to cool for 10 minutes before slicing into squares and serving warm.