Making Pumpkin Oat Crumble Muffins is a breeze! Just follow these simple steps:

1. Preheat the Oven: Preheat your oven to 350°F (175°C). Line a muffin tin with paper liners or grease it lightly.
2. Mix Wet Ingredients: In a large bowl, combine the pumpkin puree, vegetable oil, brown sugar, granulated sugar, eggs, and vanilla extract. Mix until smooth.
3. Combine Dry Ingredients: In another bowl, whisk together the rolled oats, flour, baking powder, baking soda, cinnamon, nutmeg, and salt.
4. Combine Mixtures: Gradually add the dry ingredients to the wet ingredients. Stir until just combined; do not overmix.
5. Prepare Crumble Topping: In a small bowl, mix the rolled oats, flour, brown sugar, cold butter, and cinnamon. Use a fork or your fingers to mix until crumbly.
6. Fill Muffin Tin: Divide the muffin batter evenly among the prepared muffin cups, filling each about two-thirds full.
7. Add Crumble Topping: Sprinkle the crumble topping generously over each muffin.
8. Bake: Place the muffin tin in the preheated oven and bake for 20-25 minutes, or until a toothpick inserted in the center comes out clean.
9. Cool: Remove the muffins from the oven and let them cool in the pan for about 10 minutes. Then, transfer them to a wire rack to cool completely.

Following these steps will lead you to scrumptious Pumpkin Oat Crumble Muffins that you can share with friends and family!