Preheat your oven to 350°F (175°C). This ensures that your cookies bake evenly.
In a large mixing bowl, cream together the softened unsalted butter, granulated sugar, and packed brown sugar using a whisk or an electric mixer. Beat until the mixture is light and fluffy, about 2-3 minutes.
Add the vegetable oil, large egg, and vanilla extract to the creamed mixture. Mix until well combined.
In a separate bowl, whisk together the all-purpose flour, baking soda, salt, and quick cooking oats to evenly distribute the leavening agent.
Gradually add the dry ingredient mixture into the wet ingredients, mixing until just combined. Be careful not to overmix.
Gently fold in the chocolate chips and Frosted Flakes cereal using a spatula to keep the cereal crunchy.
Using a cookie scoop or tablespoon, drop rounded portions of cookie dough onto a baking sheet lined with parchment paper, leaving space between each cookie for spreading.
Bake in the preheated oven for 10-12 minutes, or until edges are lightly golden. Centers may look underbaked but will firm as they cool.
Allow the cookies to cool on the baking sheet for about 5 minutes before transferring to a wire rack to cool completely. Enjoy!