Heat oven to 375. Mix raisins, milk, lemon juice, and rind in a saucepan; heat until bubbly. Set aside. In a large bowl, cream butter sugar, and vanilla; add dry ingredients. Add oats and nuts. Spread half of the oat mixture in a greased 9 x 13 inch pan. Pour raisin mixture over top and cover with remaining oat mixture. Bake 25 minutes or until light golden brown. Slice into bars when cool. Store in refrigerator.