Preheat oven to 350°F (175°C). Line a baking sheet with parchment paper.
In a large bowl, cream together the butter, granulated sugar, and brown sugar until smooth.
Beat in the vanilla extract and eggs until well combined.
In a separate bowl, whisk together the flour, baking soda, and salt. Gradually add to the wet ingredients, mixing until just combined.
Fold in the M&M's.
Drop by rounded tablespoonfuls onto the prepared baking sheet.
Bake for 10-12 minutes, or until edges are lightly browned. Allow cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.