Preheat oven to 425°F (220°C). Line a 12-cup standard muffin pan with paper liners.
Prepare streusel: mix 1/4 cup flour, 1/4 cup brown sugar, 2 tbsp rolled oats, 1/4 tsp cinnamon, and 2 tbsp melted butter until crumbly.
Beat cream cheese, 1/4 cup sugar, 1 tsp flour, and 1/2 tsp vanilla until silky and lump-free. Transfer to a piping bag.
Whisk dry ingredients in a large bowl. In a separate bowl, whisk pumpkin puree, brown sugar, granulated sugar, oil, eggs, and vanilla until smooth.
Fold wet ingredients into dry ingredients just until combined without overmixing.
Spoon half the pumpkin batter into muffin liners. Pipe cream cheese filling into the center, top with remaining batter, and scatter streusel generously over top.
Bake at 425°F for 5 minutes, then reduce oven to 350°F (175°C) and bake for 15 to 17 minutes until muffin tops spring back. Cool 10 minutes before serving warm!