Preheat oven to 350°F.
Use a hand-mixer on high to combine softened butter and sugar together.
Add flour, baking soda, salt, egg, and vanilla extract and combine with hand-mixer on low, trying not to overmix.
Fold in about ¾ of the Fruity Pebbles with a spatula, being careful not to crush them.
Use a large cookie scoop or tablespoon to divide cookie dough into about 12 cookies, rolling them with clean hands into balls. Place them on a large baking sheet, leaving about 1-2 inches in between each cookie.
Add the remainder of the Fruity Pebbles on top of each cookie and press them down into the dough with your hand so they stick.
Bake for 10-12 minutes and allow to cool before enjoying.