Preheat the oven to 350°F. Grease a 2 quart baking dish with butter or nonstick cooking spray.
For the filling, in a large mixing bowl combine the peaches, sugar, self-rising flour, lemon juice, and vanilla extract. Transfer the mixture to the prepared baking dish, and spread in an even layer.
For the streusel topping, in a medium mixing bowl, whisk together self-rising flour, oats, pecans, cinnamon, nutmeg, and brown sugar.
Cut in the butter with a cheese grater, pastry cutter, or forks until it resembles a crumble.
Top the filling with the streusel, ensuring the filling is fulling covered.
Bake 50-60 minutes or until golden brown. Rest 10 minutes prior to serving. If desired, serve with a scoop of vanilla ice cream or whipped cream on top.