Preheat oven to 350°. Beat butter, granulated sugar, and brown sugar at medium speed with an electric mixer until smooth. Add eggs, 1 at a time, beating until blended after each addition. Stir in vanilla.
Combine flour and next 3 ingredients. Gradually add to butter mixture, and beat until blended after each addition. Stir in semisweet chocolate, next 3 ingredients, and, if desired, peanut butter morsels. Drop by 2 tablespoonfuls onto ungreased baking sheets.
Bake at 350° for 10 to 12 minutes or until edges are browned. Cool on baking sheets 2 minutes. Remove from baking sheets to a wire rack.
