Preheat Oven: Set your oven to 350°F (175°C). Grease an 8-inch square baking dish.
Prepare Peaches: In a large bowl, toss peaches with sugar, lemon juice, vanilla, and cornstarch. Spread evenly in the prepared dish.
Make Crisp Topping: In another bowl, combine oats, flour, brown sugar, cinnamon, and salt. Add cold butter and use your fingers or a pastry cutter to work it in until the mixture is crumbly.
Assemble: Sprinkle the topping over the peaches.
Bake: Pop it in the oven for 35 minutes, or until the top is golden and the peaches are bubbling.
Cool & Serve: Let it cool for 10 minutes before serving. It’s amazing warm, especially with a scoop of vanilla ice cream!