Preheat an oven to 170 degrees C. Line a baking tray with baking paper.
In a bowl, mix the flour, bicarb soda and salt. In a separate large bowl mix the butter, 1 cup icing sugar and vanilla. The batter should not be too smooth. Stir in the flour mixture; gently stir in the oats and pecans and lightly mix until combined.
With a spoon, drop about 1 scant tablespoon of dough per cookie onto the prepared baking tray. Bake in the preheated oven until lightly browned, about 20 minutes. Let cool completely before sprinkling biscuits with icing sugar.