Preheat the oven to 350°F (175°C). Line a muffin tin with liners.
In a large bowl, mix pumpkin puree, granulated sugar, brown sugar, vegetable oil, eggs, and vanilla extract until smooth.
In a separate bowl, whisk together flour, baking soda, baking powder, cinnamon, nutmeg, and salt.
Gradually fold dry mixture into wet mixture until just combined. Do not overmix.
Prepare crumb topping by mixing oats, flour, brown sugar, and cold butter with fingers or a fork until crumbly.
Fill muffin cups two-thirds full with batter and sprinkle generously with crumb topping.
Bake for 20–25 minutes, or until a toothpick inserted in the center comes out clean.
Cool for 5 minutes in the tin, then transfer to a wire rack. Serve warm or store for later.
Notes
Customize with nuts, chocolate chips, or a cream cheese filling. Store in an airtight container for 3–4 days, refrigerate for a week, or freeze for up to 3 months.