Preheat your oven to 350°F (175°C) and grease a 9x13-inch baking pan or line it with parchment paper for easy removal.

In a medium bowl, combine the oats, flour, baking soda, and salt. Mix well and set aside.

In a large mixing bowl, cream together the softened butter, brown sugar, and granulated sugar until light and fluffy.

Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract.

Gradually add the dry ingredient mixture to the wet ingredients, mixing until just combined.

Fold in the peanut butter chips, chocolate chips, and M&M's until evenly distributed throughout the batter.

Spread the batter evenly into the prepared baking pan.

Bake in the preheated oven for 25-30 minutes, or until the edges are golden brown and a toothpick inserted in the center comes out clean.

Allow the bars to cool in the pan for about 10 minutes before transferring them to a wire rack to cool completely. Cut into squares and serve.