• Preheat the oven to 375℉/190℃. Line a muffin tin with muffin liners and set aside.

For the streusel

• Add butter, flour, oats, white sugar, brown sugar, cinnamon, and orange zest into a bowl. With your hands or a fork, combine until a crumbly streusel forms. Place in the fridge while you make the muffin batter.
  1/2 cup all-purpose flour, 1/4 cup rolled oats, 4 tbsp butter, 1/4 cup white sugar, 2 tbsp brown sugar, 1/8 tsp cinnamon, 1/2 tsp orange zest

For the muffins

• In a bowl, add the flour, oats, baking soda, baking powder, cinnamon, cornstarch, and salt. Stir to combine and set aside.
  1 1/2 cups all-purpose flour + 1 tsp for dusting, 1 cup rolled oats, 1 tsp baking soda, 1 1/2 tsps baking powder, 1/2 tsp cinnamon, 1 tsp cornstarch, 1/2 tsp salt
• In another large bowl, add the brown sugar, oil, orange juice, sour cream, orange zest, and vanilla. Whisk for 1-2 minutes to combine.
  3/4 cups light brown sugar, 1 tbsp vanilla, 1/2 cup oil, 3/4 cups sour cream, 1/3 cup orange juice, 2 large eggs, 1 1/2 tsp orange zest
• Combine the dry and wet ingredients together with a spatula just until a soft muffin batter forms. Do not over-mix!
• In the bowl with the cranberries, add 1 tsp of flour and gently dust them. Then add them into the bowl and mix in a few times. Do not over-mix!
  1 1/2 cups fresh cranberries*
• Evenly divide the batter between the liners. If using regular muffin liners, fill the liners all the way to the top. If using tulip liners, fill them halfway. Then sprinkle a generous amount of streusel on top.
• Bake for 20-25 minutes (or 25-30 if using tulip liners). The muffins are ready when a toothpick inserted in the middle comes out clean with no wet muffin batter.
• Allow to cool, then enjoy!