6 cups (1/2-inch) slices rhubarb (about 2 pounds)  | 
                                                2 1/2 cups halved strawberries  | 
                                                3/4 cup granulated sugar  | 
                                                3 tablespoons cornstarch  | 
                                                1 teaspoon grated orange rind  | 
                                                1/2 teaspoon ground cinnamon  | 
                                                cooking spray  | 
                                                2/3 cup all-purpose flour (about 3 ounces)  | 
                                                1/2 cup packed brown sugar  | 
                                                1/2 cup regular oats  | 
                                                1/4 teaspoon ground cinnamon  | 
                                                dash of salt  | 
                                                6 tablespoons chilled butter, cut into small pieces  |