In a large bowl, stir together the oats, M&M's flour, flax seed meal, brown sugar and salt. Make a well in the middle of the mixture.
In a separate bowl, whisk the egg until light and fluffy. Add the honey, oil and vanilla; whisk until well-combined. Pour the egg mixture into the well in the oat mixture. Stir until evenly combined. Pour the mixture into a 9x13-inch baking dish; pat down and spread the mixture flat, leaving at least 1-inch of space between the mixture and the sides of the dish.