Preheat your oven to 350 degrees Fahrenheit (175 degrees Celsius) and prepare muffin tins with paper liners (for 18 muffins).
Add the flour, oats, sugar, baking powder, baking soda, salt, cinnamon, nutmeg, cloves, and apples to a large bowl and mix well to combine.
In a glass measuring cup, measure out the milk and oil, add the eggs and vanilla, then whisk together with a fork to combine the wet ingredients.
Add the wet ingredients to the dry ingredients and stir gently with a silicone spatula just until combined and no streaks of flour remain.
Divide the batter between the prepared muffin cups (this recipe makes about 18 muffins), filling them only 2/3 to 3/4 full. Add a few apple pieces to the top, if you wish.
Bake the muffins at 350 degrees Fahrenheit (175 degrees Celsius) for about 18-22 minutes, or until the tops have lost their shine and a toothpick inserted into one of the muffins comes out clean.
Cool completely before enjoying.