Preheat the oven to 375°F (190°C). In a mixing bowl, toss the sliced peaches with lemon juice, granulated sugar, and finely chopped rosemary until well coated. Transfer the mixture into a baking dish, spreading it out evenly.
5 large ripe peaches
In a separate bowl, combine rolled oats, flour, brown sugar, and a pinch of salt. Use a pastry cutter or fork to cut in the cold butter until the mixture resembles coarse crumbs.
5 large ripe peaches
Sprinkle the crumble topping evenly over the peach filling, pressing it down gently to adhere slightly to the fruit.
5 large ripe peaches
Place the baking dish into the preheated oven and bake for about 40 minutes, or until the topping is golden brown and bubbling around the edges.
Remove the crumble from the oven and let it cool slightly before serving. The topping will be crisp and caramelized, while the peaches remain tender and fragrant.
