Preheat oven to 180C. Grease baking trays. Stir together the flour, oats, bicarb soda and salt; set aside.
In a medium bowl, cream together butter and brown sugar until smooth. Stir in the peanut butter and buttermilk. Gradually mix in the dry ingredients then fold in chocolate chips. Roll dough into walnut-sized balls and place them 5cm apart onto the prepared baking trays. Use a fork dipped in flour to flatten the balls slightly.
Bake for 8 to 10 minutes in the preheated oven until lightly brown at the edges. Remove from baking trays to cool on wire racks.