Brown the salted butter before mixing to deepen the nutty flavor, creating a richer, more complex taste that elevates these cookies from good to exceptional.

Refrigerate the dough for at least 30 minutes to prevent excessive spreading and ensure chewy centers with crispy edges while keeping the M&M's and chocolate chips intact.

Lightly toast both quick-cooking and rolled oats in a dry pan for 3-4 minutes before adding to the dough to enhance their nutty flavor and add depth to the cookie.

Let eggs sit at room temperature for 15 minutes before beating to ensure better emulsification with peanut butter and sugar, creating a smoother, more cohesive dough.

Remove cookies from the oven when edges are set but centers still look slightly underdone—they'll continue cooking on the hot pan and stay gloriously soft as they cool.