Preheat an oven to 325 degrees F (165 degrees C). Line a baking sheet with parchment paper.
In a bowl, mix the flour, baking soda, and salt. In a separate large bowl, mix the butter, 1 cup confectioners' sugar, and vanilla until the mixture is smooth and creamy. Stir in the flour mixture; gently stir in the oatmeal and pecans and lightly mix until combined.
With a spoon, drop about 1 scant tablespoon of dough per cookie onto the prepared baking sheet. Bake in the preheated oven until lightly browned, about 20 minutes. Let cool completely before sprinkling cookies with confectioners' sugar.