Beat butter and sugar in a large bowl with electric mixer until fluffy. Stir in corn syrup, oats and vanilla with wooden spoon.
Pat mixture evenly into prepared pan. Bake in middle of oven 16-17 minutes.
NOTE: Dough will still look moist near center. Don't over bake.
Cool in pan on rack. When cool, spread warm glaze over top. For glaze, melt chocolate chips and peanut butter in a small saucepan. Stir over low heat until chocolate melts and mixture is smooth, then spread over top of oatmeal bars.
Cool completely before cutting into bars.