Place the pecans on a sheet pan and bake for 5 minutes, until crisp. Set aside to cool. Chop very coarsely.
In the bowl of an electric mixer fitted with the paddle attachment, beat the butter, brown sugar, and granulated sugar together on medium-high speed until light and fluffy. With the mixer on low, add the eggs, one at a time, and the vanilla.
Sift the flour, baking powder, cinnamon, and salt together into a medium bowl. With the mixer on low, slowly add the dry ingredients to the butter mixture. Add the oats, raisins, and pecans and mix just until combined.
Using a small ice-cream scoop or a tablespoon, drop 2-inch mounds of dough onto sheet pans lined with parchment paper. Flatten slightly with a damp hand. Bake for 12 to 15 minutes, until lightly browned. Transfer the cookies to a baking rack and cool completely.