Preheat oven to 350 degrees F (175 degrees C). Grease cookie sheets. Stir together the flour, oats, baking 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 2 inches apart onto the prepared cookie sheets. 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 cookie sheets to cool on wire racks.
