Preheat oven to 350 degrees. Line cookie sheets with parchment paper.
Make sure you measure flour correctly. In large bowl, using a mixer, mix the brownie mix, flour, oil, and eggs until combined well, without over-mixing. Mixture will be really thick and should come together in a ball when you scoop it up or place it in your hands to make a ball.
Add chocolate chips or any add-ins now or after you've baked your cookies. I like to add chocolate chips to the tops after they've baked, but do what you like!
Using large cookie scoop, fill scoop and place 6 scoops of dough on each baking sheet. These large cookies will bake 12-15 minutes, you just want to make sure the cookies on top aren't still wet. You can touch them, and if they are too gooey, put them back in the oven for a couple more minutes. Adjust baking time for smaller cookies, if you wish to make smaller. We love the jumbo cookies!
Let cookies cool 5 minutes, then remove them with spatula to wire racks to finish cooling, unless you want them warm, then devour!
Store in airtight container up to 1 week.