Preheat your oven to 350°F (175°C). Slice the peaches and place them in a mixing bowl. Sprinkle with granulated sugar and cinnamon, then gently toss to coat the fruit evenly.
Transfer the coated peach slices into a buttered baking dish, spreading them out in an even layer.
In a separate bowl, combine the oats, flour, brown sugar, and salt. Mix until evenly distributed.
Add the cold, cubed butter to the dry mixture. Use a fork or your fingers to cut in the butter until the mixture resembles coarse crumbs, with some pea-sized pieces remaining.
Drizzle a dash of vanilla extract over the crumb mixture and mix gently to incorporate.
Spoon the crumb mixture evenly over the peaches, covering them completely.
Place the dish in the preheated oven and bake for about 40 minutes, or until the topping is golden brown and bubbling around the edges.
Remove from the oven and let it rest for a few minutes. The aroma should be inviting, with crispy topping and fragrant peaches.
Serve warm, perhaps with a scoop of vanilla ice cream or a dollop of whipped cream if desired.
