Preheat your oven to 350°F (175°C) and line a muffin tin with paper liners or grease it with cooking spray.
In a large bowl, mix together the pumpkin puree, vegetable oil, brown sugar, granulated sugar, eggs, and vanilla extract until well combined.
In another bowl, whisk together the all-purpose flour, baking soda, baking powder, ground cinnamon, ground nutmeg, ground ginger, and salt.
Gradually add the dry ingredients to the wet mixture, stirring just until combined. Be careful not to overmix, as this can make the muffins dense.
In a separate bowl, prepare the streusel topping by mixing the rolled oats, flour, brown sugar, melted butter, and ground cinnamon until crumbly.
Scoop the muffin batter into the prepared muffin tins, filling each cup about ⅔ full.
Sprinkle the streusel topping generously over each muffin.
Bake in the preheated oven for 18 to 22 minutes, or until a toothpick inserted into the center comes out clean.
Once baked, remove the muffins from the oven and allow them to cool in the pan for about 5 minutes before transferring them to a wire rack to cool completely.
Notes
Serve warm or at room temperature, optionally dusted with powdered sugar.