Preheat oven to 350 degrees. Prepare muffin pan lining a 12-cup muffin pan with cupcake liners or spray with non-stick cooking spray.
Prepare the streusel by mixing butter, flour, brown sugar, white sugar and cinnamon together until crumbly and completely combined and set aside.
In a large mixing bowl, combine 1 ½ cups flour, baking powder, salt, and brown sugar.
Then add the egg, oil, buttermilk, and vanilla, and mix until just combined.
Next add peaches and gently fold in.
Divide the muffin batter between 12 greased or paper-lined muffin cups.
Evenly sprinkle crumb topping over muffin tops.
Bake in center of oven for 18 minutes until edges are golden and a toothpick inserted into the center comes out clean.
Remove from oven and allow to cool.