Preheat the oven to 350ºF. Prepare a 10 or 12 inch skillet or 9 by 13 baking pan.
Prep Peaches: Choose peaches that are ripe but firm. Peel the skin off the peaches with a vegetable peeler (you can leave them on if you wish). Slice peaches and cut into chunks. Add the peach chunks to the skillet or pan. Top with granulated sugar, flour, lemon juice and cinnamon. Mix together until combined. Set aside.
Top Peaches: To a small bowl whisk together sourdough discard and melted butter until combined. Add brown sugar, cinnamon and salt. Mix again. Give the rolled oats a quick whirl in the blender to break them down just a bit. Add flour and oats and mix. The topping will feel a little wet and sticky. Take chunks of the oat topping and spread on top of the peaches until the entire pan is dotted with oat topping.
Bake for 50-60 minutes until peaches are bubbly and the oat topping is baked through. Let sit for 20-30 minutes and then scoop warm peach crisp onto a plate. Serve with a scoop of vanilla ice cream and enjoy!
