Step 1

Preheat oven to 350°. Combine oats, flour, walnuts, brown sugar, cinnamon, ginger, and salt in a large bowl. With your fingers, rub butter into oat mixture until blended and coarse lumps form. Cover and chill.

Step 2

Combine granulated sugar and cornstarch in another large bowl. Add raspberries and rhubarb and toss gently to combine with cornstarch mixture. Pour into a shallow 2- to 3-qt. baking dish and sprinkle evenly with topping.

Step 3

Bake crisp until topping is golden brown and fruit is bubbling, about 45 minutes. Serve warm or at room temperature, with ice cream.