Heat oven to 375°F. Grease 13x9-inch pan.
In medium saucepan, combine all filling ingredients except vanilla; mix well. Bring to a boil. Reduce heat to low; cook 10 minutes or until thickened, stirring occasionally. Remove from heat; stir in vanilla.
Meanwhile, place quick bread mix in large bowl. With pastry blender or fork, cut in margarine until crumbly. Stir in walnuts. Reserve 1 cup mixture for topping. Press remaining mixture in bottom of greased pan.
Carefully spread filling over base. In small bowl, combine reserved 1 cup of base mixture and oats; mix well. Sprinkle over filling.
Bake at 375°F. for 18 to 23 minutes or until top is golden brown. Cool 30 minutes or until completely cooled. Cut into bars.