Preheat the oven to 350°F (175°C). Line two baking sheets with parchment paper.
In a large bowl, beat together the peanut butter, softened butter, granulated sugar, and light brown sugar until creamy and smooth using an electric mixer.
Add the eggs one at a time, beating well after each addition. Stir in the vanilla extract.
In a separate medium bowl, whisk together the rolled oats, all-purpose flour, baking soda, and salt.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined.
Fold in the semisweet chocolate chips and candy-coated chocolate pieces until evenly distributed.
Using a cookie scoop or tablespoon, drop rounded balls of dough about 2 inches apart onto the prepared baking sheets.
Bake for 9 to 11 minutes, or until the edges are lightly golden but the centers remain soft.
Remove from the oven and allow cookies to cool on the baking sheets for 5 minutes before transferring to a wire rack to cool completely.