Toss together pears, 1 tablespoon no-calorie sweetener, and orange juice; spoon into a 9-inch pie plate or 4 (8-ounce) custard cups.
Stir together remaining 4 tablespoons no-calorie sweetener, flour, butter, and pumpkin pie spice. Stir in oats and chopped pecans, and sprinkle evenly over pear mixture.
Bake at 375° for 25 to 30 minutes or until top is crisp and fruit is tender. Serve warm with ice cream.