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 7x9 baking dish but an 8x8 or 9x9 baking pan works too.
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.
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.
Notes
Store baked peaches in an airtight container in the fridge for up to 5 days.