Preheat oven to 350°F and grease the sides and bottom of a 9x13-inch pan with butter.
In a large bowl, cream the softened butter and the sugars until light and fluffy.
½ cup butter, ¾ cup granulated sugar, ¾ cup brown sugar
Beat in eggs, one at a time, then add the vanilla extract.
2 large eggs, 2 teaspoons vanilla extract
Combine the flour, baking powder, and salt in a medium-sized bowl. Slowly add the dry ingredients to the creamed mixture.
1 ½ cups all-purpose flour, 1 teaspoon baking powder, ½ teaspoon salt
Mix in chocolate chips and 1 cup of the M&M's until just combined. Do not over mix cookie dough.
1 cup semisweet chocolate chips, 1 ½ cups M&M candy
Spoon the cookie dough into your 9x13 baking pan. Spread the batter evenly in the pan.
Sprinkle the remaining M&M's over the top.
1 ½ cups M&M candy
Bake at 350°F for 25-30 minutes or until golden brown.
Cool completely. Cut into bars.