combine melted butter with sugar; mix well. Add eggs, one at a time, beating well after each addition. Sift together the dry ingredients; stir into the butter mixture. Add nuts, chocolate chips, and vanilla.
Spread batter into a greased and floured jellyroll pan, 10x15x1-inch. Bake at 350° for 25 minutes.
Makes about 4 dozen bars, depending on size.