In a large bowl, combine oats, peanut butter, brown sugar, granulated sugar, melted butter, vanilla extract, baking soda, and salt. Stir until well combined.
Add in chocolate chips and peanut butter chips and mix until combined.
Using a cookie scoop, scoop out dough onto ungreased cookie sheet, about 2 inches apart.
Bake for 8-10 minutes, or until edges are golden brown.
Let cool for 5 minutes before transferring to cooling rack.
Interesting Facts
The origin of the Monster Cookie recipe is unknown, but it's believed to have originated in the United States in the 1960s.
Monster Cookies are a popular treat for children's birthday parties.
Monster Cookies are a great way to use up leftover candy and chips.