Preheat oven to 350 degrees. Coat 12-cup muffin tin with cooking spray and set aside.
In a large bowl, mix together the flour, butter, sour cream, sugar, and vanilla. Gently fold in the peaches.
Divide the batter evenly among the muffin tin cups. Bake until golden and a toothpick comes out clean from muffin center, about 30-35 min.