Preheat oven to 400 degrees F (205 degrees C). Line a muffin tin with cupcake papers or spray with butter flavored non stick spray. Set aside.
In a mixing bowl, let the Butter (1/2 cup) cool slightly. By hand, stir in Buttermilk (1 cup), Egg (1), and Vanilla Extract (1/2 teaspoon) until well combined.
In a separate bowl combine Quaker Oats® Old Fashioned (1 cup), All-Purpose Flour (1 cup), Brown Sugar (1/2 cup), Baking Powder (1/2 teaspoon), Baking Soda (1/2 teaspoon), Ground Cinnamon (1 teaspoon), Salt (1/2 teaspoon), Ground Nutmeg (1/2 teaspoon), and Ground Allspice (1/4 teaspoon).
Gradually add the dry ingredients into the wet mixture. Stir until the batter is just combined, do not overstir.
Gently fold in the Apple (1).
Spoon the mixture into the muffin pan, filling each cup two thirds full.
Bake for 20 minutes, or until a toothpick inserted in the middle is clean.
Serve warm with butter and enjoy!