Line an 8 x 8 pan with parchment paper and then lightly spray the paper with nonstick spray. This will help in easy removal of the brownies.
Preheat the oven according to brownie mix instructions.
In a large bowl, prepare the brownies according to the brownie mix instructions.
Coarsely chop or crush the Oreos. You can crush or chop them as large or as fine as you like. I like some bigger chunks in these brownies.
Mix the chopped oreos and 1/3 cup of the M&M's into the batter.
The batter will be thick! Pour the batter into the prepared pan and sprinkle the remaining 1/3 cup of M&M's evenly over the top of the brownies.
Bake according to the directions for an 8 x 8 pan. Ever so slightly under-baking these brownies makes them ultra fudgy and keeps the cookies softer throughout the batch.