Mix the sugar and peanut butter with a hand or stand mixer on medium speed for 5 minutes.
Mix in the vanilla. Add the flours, baking soda, and baking powder and mix on medium speed. Add the oats and mix for a few seconds. This will be stiff. Add the milk and mix on medium until just combined.
Fold in the peanuts and dates and make sure everything is well incorporated.
You can use your hands to press the dough lightly into the prepared dish. Bake for 15 to 20 minutes or until lightly golden brown.
Place on a wire rack to cool. Cut into sixteen squares and store in the refrigerator.