Preheat oven to 350°F. For the Peach Blueberry Filling, toss fruit with lemon juice and vanilla in large bowl. Mix cornstarch and 2 teaspoons cinnamon in small bowl. Sprinkle over fruit; toss to coat well. Spoon into lightly greased 11x7-inch baking dish.
For the Streusel Topping, mix flour, oats, brown sugar and 1 teaspoon cinnamon in medium bowl. Cut in butter with pastry blender or 2 knives until coarse crumbs form. Sprinkle evenly over fruit.
Bake 40 to 45 minutes or until fruit is tender and topping is golden brown. Serve warm with ice cream or whipped cream, if desired.