Crust/Topping:
1 cup old fashioned rolled oats
1 cup all purpose flour
2 teaspoons cinnamon
1/3 cup brown sugar, packed
1/2 teaspoon salt
4 ounces (1 stick) unsalted butter, cold, and cut into 1/4″ cubes
For the filling:
1 3/4 cups rhubarb (2 large stalks or 8 ounces), red outer layer removed, halved lengthwise and cut into 1/2″ chunks
2 cups fresh raspberries (8 ounces)
1/4 cup brown sugar, packed
1/4 cup granulated sugar
zest of one medium orange
2 tablespoons fresh orange juice
2 tablespoons cornstarch
1 tablespoon grated fresh ginger

Preheat the oven to 350 degrees. Line an 8×8″ square baking dish with parchment paper so that it hangs over the sides and using scissors, cut a diagonal line from each corner of the parchment down to the each corner of the pan so that the parchment fits snugly. Spray the parchment with cooking spray and set aside.
Prepare the crust/topping:
In a medium bowl, stir together the oats, flour, brown sugar, cinnamon, and salt. Cut in the butter using a pastry blender, two forks, or your hands until the mixture resembles a coarse meal and the dough is pea-sized pieces. Press 2/3 of the crust-topping into the prepared pan and bake for 15 minutes or until light golden brown. Cool slightly on a wire rack.
Prepare the filling:
Place the rhubarb, raspberries, brown sugar, granulated sugar, orange zest, orange juice, cornstarch and ginger in a medium bowl and stir to combine. Pour over the crust and spread evenly. Sprinkle the remaining 1/3 of the crust/topping over the fruit, and bake for 40-45 minutes, or until bubbly and golden brown. Cool on a wire rack, then place in the refrigerator for 4-6 hours or overnight to set. Cut into squares and enjoy cool, or heated with ice cream!