Preheat the oven to 375 F. Grease a 10 x 13-inch pan.
Pulse the oats in a food processor or blender until they form a coarse flour.
Combine the oats, flour, baking soda and salt in small bowl.
Cream the butter in the bowl of a mixer. Add the apple sauce, granulated sugar, brown sugar and vanilla extract. Add eggs, one at a time, beating well after each addition. Gradually beat in flour mixture. Fold in the dark chocolate chunks and nuts. Spread into the prepared pan.
Bake for 20 to 25 minutes or until golden brown.
Cool in pan on wire rack.
Cut into bars for serving.