Preheat oven to 350°F. Line baking sheets with parchment, if desired.
In a large bowl or stand mixer, beat together peanut butter, sugars, and butter until fluffy. Mix in vanilla and eggs.
Sift together oats and baking soda, then mix into butter mixture. Stir in M&Ms and chocolate chips.
Scoop dough into balls about 3 tablespoons big and place on baking sheets about 2 inches apart.
Bake 12 minutes. Let rest on baking sheets 3 minutes before carefully transferring to a wire rack to finish cooling. Repeat with remaining cookie dough.
Notes
Makes 24 large cookies.
For smaller cookies, use a medium cookie scoop (about 1 ½ tablespoons).