In a large bowl, whisk together the flour, baking powder, baking soda and salt. Set it aside.

In a seperate large bowl, use a hand mixer or a stand mixer with the paddle attachment to beat the butter until it is smooth and creamy. Then beat in both sugars. Once they're combined, beat in the eggs, vanilla and peanut butter, scraping down the sides as needed.

Beat in the oats, then on low speed beat in the M&Ms and chocolate chips until it's all just combined. Then cover the dough and place it in the fridge to chill for 20 minutes and up to 4 days. If chilling the dough for longer than 1 hour, then just leave it out for about 30 minutes before scooping it out.

Preheat the oven to 350°F. Line a few large baking trays with parchment paper or silicone baking sheets and set them aside. Once the dough has chilled, scoop it out (about 2 tbsp. of dough per cookie) and roll into balls. Place them about 3" apart on the tray.

Bake for 11-14 minutes, until the edges are lightly browned. Let them cool for about 5 minutes on the tray, then transfer them to a wire rack to cool completely.