To prepare a whole wheat oatmeal chocolate chip muffins recipe, first you need to prepare your ingredients. First, you'll need your flour, baking powder, sugar, salt, and cocoa powder. Then, add your wet ingredients to the dry ingredients and mix until everything is evenly combined. Next, preheat your oven to 350 degrees F (180 degrees C) and grease your muffin tins with cooking spray. In another large bowl, mix together your chocolate chips, butter, brown sugar and vanilla extract. Pour the batter into the muffin pans and bake for 18 to 20 minutes or until the tops are golden brown. Remove from the oven and let cool for 5 minutes before serving.