Using a hand mixer, cream the butter and both brown and white sugars together for 1 minutes until creamy and smooth.
Add the egg, vanilla and molasses; beat until well combined.
In a separate bowl, stir the oats, flour, baking soda, cinnamon, and salt together until well combined.
Add the wet ingredients to the dry and mix until combined.
Add the m&m's and stir to combine.
Place the dough in the refrigerator for 30-60 minutes to prevent the cookies from spreading too much while baking.
Preheat the oven to 350 degrees. Line a baking sheet with parchment paper.
Scoop spoonfuls (about 1 ½ tbsp) of the dough onto the baking sheet placing them 2 inches apart.
Place into the oven and bake for 9-11 minutes, or until set.
Remove from the oven and immediately sprinkle a extra m&m's on top of each cookie, if desired. Don’t over load them but this will make the cookies look extra pretty.
Allow them to set for 5 minutes before moving them to a wire rack to finish cooling. Serve with ice cold milk and enjoy.