1-Preheat oven to 350F: Preheat oven to 350F. Slice the peaches in half vertically, twist the halves apart, and remove the pit. Arrange cut-side up in a baking dish. I used a 7×9 baking dish but an 8×8 or 9×9 baking pan works too.
2-Whisk flour, oats, brown sugar, and cinnamon: Whisk flour, oats, brown sugar, and cinnamon together in a small bowl. Using a fork, cut in the cold butter until small crumbs form. Generously spoon the crumble topping to the center of each peach.
3-Bake for about 15-20 minutes, or until: Bake for about 15-20 minutes, or until peaches are tender and the crumble is golden brown. Remove from oven and let cool slightly before serving.