Place the pecans on a sheet pan and bake for 5 minutes, until crisp. Set aside to cool. Chop very coarsely.
Beat the butter, brown sugar, and granulated sugar together on medium-high speed until light and fluffy. Add the eggs, one at a time, and the vanilla.
Sift the flour, baking powder, cinnamon, and salt together into a medium bowl. Slowly add the dry ingredients to the butter mixture. Fold in the oats, raisins, and pecans with a rubber spatula 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.