Preheat the oven to 400°F.
In a casserole dish or cast-iron skillet, add the sliced peaches, sugar, vanilla, cornstarch and cinnamon and mix until the peaches are fully coated.
In a separate bowl, combine the flour, oats, brown sugar, cinnamon, pecans, and salt.
Add in the cold cubed butter with your hands or a dough blender and mix until the mixture is crumbly. (Don’t overmix — you still want some chunks of butter. It should be crumbly, not smooth.)
Add the crisp topping over the peaches, sprinkling evenly over all the peaches.
Bake at 400°F for 40-45 minutes, until the topping is golden brown and juices are bubbling around the edges. Remove it from the oven and cool it for 5 minutes.
Serve warm with vanilla ice cream, yogurt, or plain.