Preheat the oven to 350 degrees F (175 degrees C). Line a baking sheet with parchment paper.
Beat butter, white sugar, and brown sugar in a large mixing bowl until creamy. Mix in flour and oil until combined. Add oats, rice cereal, coconut, eggs, vanilla, baking soda, cream of tartar, and salt; mix until well blended. Mix in walnuts and chocolate chips. Drop tablespoonfuls of dough 2 inches apart onto the prepared baking sheets.
Bake in the preheated oven until edges are golden, 10 to 15 minutes. Cool on the baking sheet briefly before removing to a wire rack to cool completely.
