Preheat the oven to 350°F (175°C). Lightly grease a 9-inch pie dish or baking dish.
Make the crisp topping: In a medium bowl, whisk together the flour, brown sugar, cinnamon, and salt. Cut in the cold butter until the mixture resembles coarse crumbs. Stir in the oats and chopped nuts, then refrigerate while you prepare the filling.
Make the peach filling: In a large bowl, gently toss the sliced peaches with the brown sugar, flour, cinnamon, ground ginger, nutmeg, lemon juice, and vanilla until evenly coated.
Assemble: Spread the peach filling into the prepared baking dish. Sprinkle the chilled crisp topping evenly over the peaches.
Bake for 45–50 minutes, or until the topping is golden brown and the filling is bubbling around the edges.
Cool for 10–15 minutes before serving. Enjoy warm with vanilla ice cream or whipped cream, if desired.
Notes
Use ripe but firm peaches for the best texture.
Keep the butter cold for a crisp, crumbly topping.
If your peaches are extra juicy, add 1 tablespoon of flour to the filling.
Bake until the filling is bubbling around the edges, not just until the topping is golden.
Let the peach crisp cool for 10–15 minutes before serving so the filling can thicken.