In a very large mixing bowl, beat butter with an electric mixer on medium to high speed for 30 seconds. Add oil, granulated sugar, brown sugar, baking soda, vanilla and salt. Beat on medium speed until mixture is combined, scraping sides of bowl occasionally. Add eggs one at a time, beating on medium speed after each addition until combined. Add flour one cup at a time, beating on low speed and adding as much of the flour as you can with the mixer. Stir in any remaining flour with a wooden spoon until combined. Stir in chocolate pieces.
Drop dough by rounded tablespoons or by using a rounded #40 ice cream scoop 2 inches apart onto ungreased cookie sheets. Bake in a 350 degree F oven for 9 to 11 minutes or until edges are light brown and centers are set. Cool on cookie sheets for 2 minutes. Transfer to wire racks and let cool. Makes about 80 cookies.