Pre-heat the oven to 350 degrees.
In a large bowl, beat together the butter, brown sugar, eggs, and vanilla.
In a small bowl, mix together the flour, baking powder, baking soda, cinnamon, nutmeg, and oats.
Add the dry ingredients to the large bowl of wet ingredients and mix just until blended.
Add in the carrots, pecans, and the raisins and stir to combine. This dough will be sticky.
Place the dough in the refrigerator for 15 minutes.
Line a baking sheet with parchment paper and scoop cookies on the sheet 2" apart. I use a golf-ball sized cookie scoop so they are all the same size. Since this is a sticky moist dough, I wouldn't recommend using your fingers to scoop the dough. Bake for 12-14 minutes until you see tiny bubbles start forming on the tops of the cookies and the edges start to darken slightly. Let the cookies cool completely before icing.