Cream together butter, sugar, eggs and vanilla until light and fluffy. Beat in peanut butter. Sift together flour, soda, and salt. Add to creamed mixture. Add oatmeal, if desired. Shape dough into 1" balls. Place on greased cookie sheet and flatten to about 1/2" with fork tines in criss-cross pattern. Bake at 375 degrees for 8 to 10 minutes. Makes 76 cookies.