Add the oats, peanut butter, protein powder, flaxseed, honey, and vanilla in a large bowl. Stir to combine.
Slowly add 1 tablespoon of liquid at a time until mixture can hold together. Depending on how drippy your peanut butter is, you may need more or less liquid.
Scoop tablespoon size servings of mixture and roll into balls. Wet hands with water to roll dough if it is too sticky. Place in a single layer on wax paper. Store in a sealed container in fridge for up to a week. Freeze for up to a month.
