Preheat oven to 350°F. Grease a 2½ quart baking dish.
In a large bowl, add raspberries, sugar, and ¼ cup flour. Gently toss to combine. Add to prepared baking dish.
In a medium bowl, mix together oats, ⅓ cup flour, brown sugar, and cinnamon. Using a pastry cutter, or two forks, cut butter into the oat mixture. Continue until it resembles coarse crumbs.
Sprinkle the oat mixture over the berry mixture.
Bake for 25 minutes, or until golden brown and lightly bubbling.
Notes
If using a 9 inch baking dish, bake at 350°F for 30 minutes or until golden brown and lightly bubbling.