1. Preheat oven to 350ºF. Butter a deep 9-by-13-inch baking dish. Make topping: In a bowl, combine flour, sugar, brown sugar and salt. Rub in butter with fingertips until mixture forms pea-size lumps. Stir in oats and pecans.
2. Make filling: In a large bowl, mix together apples, pears and cranberries. Remove zest from orange and squeeze juice; add both to bowl. Stir in cornstarch and sugar. Pour into baking dish, sprinkle with topping and bake until filling is bubbling and topping is golden brown and crisp, about 1 hour 15 minutes.