In bowl, toss together pears, apples, flour, sugar, lemon juice and cinnamon until combined; spread in 8-inch (2 L) square glass baking dish. Set aside.
Topping: In small bowl, whisk together oats, sugar, flour and nutmeg; drizzle with butter, tossing with fork until crumbly. Sprinkle over pear mixture.
Bake in 350°F (180°C) oven until pears are tender and topping is golden and crisp, about 1 hour.
