Preheat the oven to 190 degrees C. Grease baking trays.
In a large bowl cream the butter and the sugars using an electric mixer. Mix in the eggs, vanilla and coffee flavoured liqueur.
Measure the oats and blend in a blender to a fine powder. In a separate bowl mix together the flour, oats, baking powder, bicarb soda and salt. Stir the dry ingredients into the butter mixture until blended, then stir in the Smarties. Roll into balls and place 5cm apart on baking trays.
Bake for 10 to 12 minutes in the preheated oven until the edges start to turn golden.