In a large mixing bowl, add old-fashioned oats, peanut butter, honey, butterscotch chips, and chopped walnuts. Mix well until everything is thoroughly combined.

Cover the mixing bowl with plastic wrap and place it in the fridge. Let it chill for at least 1 hour or overnight until the mixture is firm.

Once chilled, take the mixture out and shape it into small, compact balls, about an inch in diameter.

Line a baking sheet with parchment paper and place the finished balls on it to avoid sticking.

Transfer the protein balls to an airtight container or ziplock bag. Store them in the refrigerator for up to 2 weeks.