Preheat oven to 350 degrees
Add water to ground flax seed, and stir together until mixed. Set aside.
In an electric mixer, cream butter, sugar, and brown sugar.
Mix in eggs and vanilla.
Add flax seed mixture, flour, brewer's yeast, baking soda, and salt. Mix until well combined.
Fold in oats and stir. Once the oats are well combined, add M&Ms and chocolate chips.
Place spoonfuls of dough onto a baking sheet.
Bake for 10-13 minutes until the edges are starting to brown.
After removing the baking sheet from the oven, let the cookies rest for several minutes, and move to a wire rack to cool completely.