Cream the butter, brown sugar, and sugar in a mixing bowl until light and fluffy, using an electric mixer at medium speed. Beat in the egg and vanilla. Blend in the peanut butter. Sift the flour, baking soda and salt together. Stir the dry ingredients into the creamed mixture, blending well. Stir in the oats. Spread the mixture in a greased 13 X 9 X 2-inch baking pan. Sprinkle with the chocolate chips. Bake in a 350 degree F. oven for 25 minutes or until done. Cool in the pan on a rack. While still warm drizzle with the vanilla glaze. When cooled, cut into 48 (2 X 1 1/2-inch) bars.

Vanilla Glaze:

Combine all of the ingredients in a bowl and beat, with an electric mixer set to high speed, until smooth.