Preheat the oven to 190 degrees C. Lightly grease baking trays.
In a large bowl, mix together the oil, margarine, brown sugar and white sugar until smooth. Beat in the eggs one at a time then stir in the vanilla.
Combine the flour, bicarb soda, baking powder and salt; stir into the sugar mixture. Mix in the cornflakes, oats, chocolate chips and walnuts. Drop by heaping teaspoonfuls onto the prepared baking trays.
Bake for 12 to 15 minutes in the preheated oven, until golden brown. Allow biscuits to cool slightly on the baking trays before removing to wire racks to cool completely.