"This is one of my favorite protein bar recipes. They are so much cheaper than commercial bars, very healthy, and better-tasting. Kids love them (provided they like peanut butter)! Plus you know what the ingredients are. You can add anything - raisins, cranberries, dark chocolate nibs, coconut, etc. Keep refrigerated."
Line a 9x11-inch baking pan with parchment paper, leaving a 2-inch overhang on two sides.
Place peanut butter, protein powder, and honey in a large bowl; mix with a wooden spoon to combine. Add goji berries, flax seeds, and oats, stirring well to combine. Spread mixture evenly in baking pan.
Place baking pan in the refrigerator and chill until mixture is set, about 1 hour. Lift out of the baking pan; cut into 3-inch squares.