Preheat the oven to 375 F. Grease an 8 x 8 glass baking dish and set aside. Toss together the rhubarb, strawberries, cornstarch and granulated sugar until coated. Dump the mixture into the greased baking pan and set aside.
In a medium bowl stir together the flour, oatmeal, brown sugar, salt. Cut in the cold butter with a pastry blender. Continue working in the butter until it clumps together into crumbs. Top the strawberries and rhubarb with the crumble.
Bake in a 375 F oven for 30-35 minutes or until crumble is browned and filling is bubbly. Serve warm with ice cream or whipped cream