01 - Preheat oven to 350°F. Grease and line a 9x5-inch loaf pan with parchment paper, ensuring an overhang for effortless removal.
02 - Whisk together flour, oats, baking powder, baking soda, salt, and ground cinnamon in a medium mixing bowl. Set aside.
03 - In a large bowl, use an electric mixer or whisk to cream butter, vegetable oil, brown sugar, and granulated sugar until pale and fluffy, approximately 2–3 minutes.
04 - Add eggs one at a time into the creamed mixture, mixing thoroughly after each addition. Blend in vanilla extract and creamy peanut butter until smooth.
05 - Gently stir the dry ingredients into the wet mixture, mixing just until incorporated. Avoid overmixing to maintain loaf tenderness.
06 - Carefully fold semisweet chocolate chips and candy-coated chocolate pieces into the batter.
07 - Transfer batter into the prepared loaf pan, smoothing the top. Mix granulated sugar with ground cinnamon for the topping and sprinkle evenly over batter surface.
08 - Bake for 50–55 minutes, or until a toothpick inserted into the center yields a few moist crumbs.
09 - Let the loaf cool in the pan for 15 minutes. Remove using the parchment overhang and cool completely on a wire rack before slicing.