Preheat your oven to 375°F (190°C). In a large bowl, gently toss the sliced peaches with lemon juice, granulated sugar, and cinnamon until evenly coated. Transfer the mixture into a buttered baking dish, spreading it out to form an even layer.
In a separate bowl, combine the oats, flour, brown sugar, and a pinch of salt. Use a pastry cutter or fork to cut the cold, cubed butter into the dry ingredients until the mixture resembles coarse crumbs with some larger pea-sized pieces.
Sprinkle the crumble topping evenly over the peaches, covering the surface completely for a crispy top layer.
Place the baking dish in the preheated oven and bake for about 40 minutes, or until the topping is golden brown and the fruit is bubbling around the edges.
Remove the peach crumble from the oven and let it cool slightly; the filling should be thickened, and the topping crisp and fragrant. Serve warm, optionally with a scoop of vanilla ice cream or a dollop of whipped cream.
