01 -
Get your oven going at 350°F (177°C). Lightly grease a 9×13-inch dish to keep things from sticking when you bake.
02 -
Combine the cake mix, eggs, oil, and vanilla in a big bowl until it looks like a thick, sticky dough. Gently stir in the M&Ms and chocolate chips so they’re spread out nicely.
03 -
Press the dough evenly into the greased dish and smooth the top. Toss it in the oven for 20-25 minutes, or until the edges are a nice light brown and the center is barely firm. Don’t cook too long if you like them soft!
04 -
Leave the cookie bars in the pan until they cool down all the way. Once they’re set, cut them into squares and dig in.