Preheat your oven to 350 degrees Fahrenheit and prepare a large muffin tin with 12 muffin cups.
Add the flour, baking powder, salt and sugar to a large bowl and whisk together to combine.
Add the peaches and stir well to coat.
Add the milk, egg and oil and stir together with a rubber spatula just until the flour disappears.
Portion the batter out into the muffin cups evenly (about 3/4 full).
-For the topping
Combine the flour, sugar and cinnamon and baking powder in a small bowl and stir.
Add the cold butter in chunks and break it up with your fingers in the flour mixture until it resembles coarse crumbs.
Top the muffins with a spoonful of the streusel topping.
Bake at 350 degrees Fahrenheit for about 20 minutes until golden brown and a toothpick inserted into one of the muffins comes out clean.
Store in an airtight container for up to 3 days.
