Line a 13x9 inch baking pan with aluminum foil and spray generously with non-stick spray. Preheat oven to 350 degrees.
In a medium bowl, whisk together the flour, baking soda, and salt. Set aside.
In the bowl of a stand mixer, cream together the butter and both sugars until creamy.
Add the eggs, one at a time and blend after each one.
Add the vanilla and blend together.
Gradually add the flour mixture and blend well together.
By hand, stir in the M&M candies and chocolate chips.
Spread cookie dough into prepared pan evenly. Bake for 35-40 minutes or until baked through. Allow to cool completely before cutting into squares.