Preheat oven to 425°F. Lightly grease a large baking sheet or line with parchment paper; set aside. In a medium bowl stir together all-purpose flour, whole wheat flour, baking powder, the 1 to 2 teaspoons chili powder, the salt, and oregano. Make a well in the center of the flour mixture.
In a small bowl whisk together sour cream and milk until smooth. Add sour cream mixture all at once to flour mixture; stir just until combined.
Using about 1/3 cup dough for each biscuit, drop dough into eight mounds onto prepared baking sheet, leaving about 2 inches between mounds. If desired, sprinkle with additional chili powder. Bake for 14 to 16 minutes or until golden brown. Serve warm.