Beat 1 cup butter, 2/3 cup powdered sugar and vanilla with a mixer until light and fluffy. Beat in 1 1/2 cups flour on low speed until just combined. Press dough firmly onto the bottom of a greased jelly-roll (15x10) pan. Bake at 375º for 20 minutes or until golden. Let cool and set aside.
Combine berries, sugar, cornstarch and water in a saucepan. Heat to boiling, stirring frequently; boil for 1 minute. Remove from heat and set aside.
Combine oats, remaining flour, brown sugar, and cinnamon in a medium bowl. Cut in butter until mixture resembles coarse brumbs. Set aside.
Spread berry mixture over cooled crust. Sprinkle oat mixture over berries.
Bake at 375º for 35-40 minutes or until berry mixture bubbles and top is golden.
Cool completely in pan on wire rack. Sprinkle with remaining powdered sugar. Cut into bars.