1. Preheat your oven to 375 F (190 C). Line a 12-cup muffin tin with paper liners or grease it thoroughly with non-stick spray.

2. In a large mixing bowl, whisk together the old-fashioned rolled oats, all-purpose flour, brown sugar, baking powder, baking soda, ground cinnamon, ground ginger, ground nutmeg, ground cloves, and salt. Make sure there are no lumps of brown sugar and all the spices are evenly distributed.

3. In a separate medium bowl, combine the pumpkin puree, milk, vegetable oil (or melted coconut oil), large egg, and vanilla extract. Whisk these ingredients together until they are well combined and smooth.

4. Pour the wet ingredient mixture into the bowl with the dry ingredients. Using a spatula or a large spoon, gently mix until just combined. Be careful not to overmix; a few lumps are perfectly fine and will result in a more tender muffin.

5. Divide the batter evenly among the 12 prepared muffin cups. Each cup should be about two-thirds full.

6. Place the muffin tin in the preheated oven and bake for 20-25 minutes, or until the tops are golden brown and a wooden skewer or toothpick inserted into the center of a muffin comes out clean.

7. Once baked, remove the muffin tin from the oven and let the muffins cool in the tin for about 5 minutes. Then, transfer them to a wire rack to cool completely.