Preheat oven to 375. Grease a jelly roll pan. Beat together butter and sugars until creamy. Add egg and beat well. Add 1/2 cup peanut butter and beat until incorporated. Sift together baking soda, salt, and flour in another bowl.
Stir into the creamed mixture; add vanilla and stir in oats. Pour into prepared pan. Bake 10-15 min. Cool briefly then cover with chocolate frosting mixed with 2 T peanut butter.