Heat oven to 350°F. Grease bottom and sides of 8-inch square (2-quart) glass baking dish with butter or cooking spray.
In large bowl, stir together 1/2 cup brown sugar, 3 tablespoons flour, 1/2 teaspoon cinnamon and the nutmeg. Add pears, cranberries and rum; stir to coat fruit with sugar mixture. Spread in baking dish.
In medium bowl, mix 1/2 cup flour, 1/2 cup brown sugar and 1/2 teaspoon cinnamon. Cut in butter, using pastry blender or fork, until mixture looks like fine crumbs. Add oats; stir until crumbly. Sprinkle evenly over fruit mixture.
Bake 40 to 45 minutes or until pears are tender when pierced with a fork and topping is golden brown. Serve warm or at room temperature.