1. Preheat oven to 350°.
2. To prepare topping, weigh or lightly spoon flour into a dry measuring cup; level with a knife. Combine flour, oats, and brown sugar in a medium bowl. Cut in butter with a pastry blender or 2 knives until mixture resembles coarse meal. Cover and chill until ready to use.
3. To prepare filling, combine cranberries and next 4 ingredients (through cornstarch) in a medium saucepan. Bring to a boil over medium-high heat, stirring constantly. Reduce heat; simmer 5 to 8 minutes or until cranberries pop. Remove from heat. Stir in vanilla; pour mixture into an 8-inch square metal baking pan coated with cooking spray. Sprinkle topping over cranberry filling. Bake at 350° for 40 minutes or until bubbly and topping is browned. Cool at least 15 minutes in pan on a wire rack. Serve with ice cream.