Line an 8 x 8 pan with parchment and spray with non-stick spray.
Cream together the butter and sugars. Blend in beaten egg and vanilla extract.
Combine flour, oatmeal and baking soda together, then mix into the butter mixture
By hand, stir in ¾ cup of M&M’s. Pat into 8 x 8 pan lined with parchment or aluminum foil. Top with remaining 1/4 cup M&M’s pushing them very slightly in to batter.
Bake at 350 for 25-30 minutes until toothpick comes out clean.
I am not a health professional and nutrition data is calculated programatically. Accuracy may vary with product selection, calculator accuracy, etc. Consult a professional for the best information.