Preheat oven to 350°F. Toss pear slices with lemon juice and vanilla in large bowl. Mix cornstarch, cinnamon and ginger. Sprinkle over pears; toss to coat well. Spoon into lightly greased 8- or 9-inch square baking dish
For the Streusel Topping, mix flour, oats, sugar and cinnamon in medium bowl. Cut in butter with pastry blender or 2 knives until coarse crumbs form. Sprinkle evenly over pear mixture
Bake 40 to 45 minutes or until pears are tender and topping is golden brown. Serve warm.