Preheat the oven to 350°F.
In a small bowl, prepare the filling: sliced peaches, maple syrup, cinnamon, vanilla extract, and corn starch. Pour the mixture into a cast-iron. (If you are making your Peach Crisp in a baking dish (9 x 9 works best), you can prepare the filling directly in the baking dish.
In a medium-sized bowl, combine all the ingredients listed above for the crust. Mix well until all of the oats are evenly coated and the mixture is moistened thoroughly.
Spread the crust mixture evenly over the filling, making sure it is distributed evenly. Bake for 35 minutes or until the filling is bubbling and the crust is golden.
Remove from the oven and let rest for 5 minutes. Serve with your favorite vanilla ice cream or whipped cream!