Preheat oven to 350℉
Whisk together oats, flour, brown sugar, and salt
Add butter and cut with forks until texture is crumbly.
In a separate bowl, add blackberries, peaches, sugar, flour, and lemon juice. Stir to combine.
Lightly grease a 9x13 inch pan and spread fruit mixture on bottom.
Sprinkle crisp topping evenly on top.
Bake for 45 minutes until topping is golden.
Let cool and serve with vanilla ice cream or whipped cream if desired.