Preheat the oven to 375 degrees F and grease a 2-quart baking dish.
Cut unpeeled peaches into ½-inch slices and place them in a large mixing bowl.
Add sugar, lemon juice, cornstarch, and salt to the peaches and stir gently using a soft silicone spatula.
Transfer the peaches to the prepared baking dish and gently pat them down to create an even layer.
In a medium-sized bowl, stir together the oats, flour, brown sugar, cinnamon, and salt.
Cut the cold butter into cubes and using a pastry cutter mix the cubes into the dry ingredients until the mixture resembles a crumble-like topping.
Sprinkle the crumble over the peaches, making sure that the peaches are covered.
Place the baking pan in the oven and bake for 45 minutes or until the top is golden brown and the peaches are bubbling.
Allow to cool before serving.