In a large bowl or stand mixer, beat the butter for 2 minutes, scraping the sides and bottom.

Add the brown sugar, white sugar, and peanut butter. Beat until incorporated.

Add 2 eggs and vanilla. Beat well, scraping sides and bottom.

Add flour but don't mix it in. Use a small spoon to stir the baking soda and salt into the flour, then beat in gently. There should still be flour streaks.

Add the quick oats, old fashioned oats, and M&Ms. Stir until incorporated but do not over mix.

Cover the bowl and chill the dough in the fridge for 1-3 hours (or overnight).

When the dough is chilled, preheat the oven to 350 degrees F. Line 2 baking sheets with silicone baking mats or parchment paper.

Use a large cookie scoop to shape the cookies. (You want cookie dough balls about 2 inches across.) Place on the baking sheet at least 2 inches apart from each other.

Bake the cookies at 350 for 10-12 minutes until the centers are alllmost done being shiny. The edges should be firm. Do not over bake.

Immediately press more M&Ms and a few candy eyes into the top of each cookie. If you want really tall, chewy cookies, take a spoon and push the edges in toward the middle on each cookies. Check this post for more details.

Let cool on the sheet for 5 minutes before removing to a cooling rack. You should definitely eat at least one of these warm. Or maybe 2 or 3. 

Store covered on the counter!