Add all the streusel ingredients to a small bowl and combine them with a pastry cutter until the mixture is well combined and is clinging together in clumps. Alternatively, you can mix the streusel in a stand mixer fitted with the paddle attachment.

Preheat the oven to 350°F and line 15 muffin tins with paper liners or spray with nonstick cooking spray.

Place the peeled, pitted, and chopped peaches into a bowl and pulse them with an immersion blender until they are in small and medium pieces. You can purée them if you prefer.

Whisk together the flour, cinnamon, baking soda, and salt in a medium bowl until everything is well combined.

Beat the eggs in a large bowl until they’re smooth, then add the sugar and whisk until dissolved. Slowly pour in the oil, whisking continuously, until all the oil has been added and is emulsified into the mixture.

Pour the dry ingredients into the wet ingredients and whisk or fold gently to combine. Be sure there are no pockets of unincorporated flour in the batter. Fold in the fresh peaches.

Fill the prepared muffin tins about ¾ full with the batter, then scatter the streusel evenly on top. Don’t be too generous with the streusel, as too much streusel will cause the muffins to sink in the center. Bake at 350°F for 20 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs attached.

Let the muffins cool in the tins for 10 minutes, then let them finish cooling completely on wire racks. Enjoy these peach muffins fresh with a little butter or an iced coffee!