In a large mixing bowl, stir with a wooden spoon peanut butter, brown sugar and Stevia. Add egg and stir well.
Add baking soda and stir well. Add oats and dried cranberries and stir well.
Cover the bowl with dough with saran wrap and place in fridge for at least 30 minutes or as long as 2 days.
Preheat oven to 350 degrees F.
Line a baking sheet with parchment paper.
Scoop cookie dough with 1 and 1/2 tablespoon size cookie scoop. Place in your hands and roll into a ball. Place on a prepared cookie sheet and gently flatten with your fingers, a fork or the bottom of a glass. Space cookies 2" apart on the sheet.
Bake cookies for 8 to 10 minutes or until golden brown.
Cool cookies on baking sheet for 5 minutes, then transfer onto cooling rack to cool completely.
These cookies are a great addition to a lunchbox, however, please be advised that it contains peanut butter. If your school has a no peanut butter policy, it's better to keep them as an after-school snack.