1. Preheat the oven to 190degC, with the rack just below the middle.
2. Measure the oats into a food processor fitted with the chopping blade and process until they resemble coarse flour. Transfer the processed oats to a large bowl and add the wholemeal flour, baking soda (make sure there are no lumps), salt, chocolate chips, sultanas and walnuts, and stir to combine.
3. Put the oil, egg and the sugars in the food processor and process until pale and creamy-looking. Add the vanilla and process again to mix.
4. Pour this mixture into the dry ingredients and stir until thoroughly combined.
5. Using two spoons, drop small walnut-sized piles of the mixture oven sheets lined with baking paper, leaving 4-5cm between each pile to allow spreading as they cook.
6. Place one tray at a time in the middle of the oven and bake for 10-12 minutes until golden brown. Cool the cookies on a wire rack. Store in an airtight container.

Makes 30-36