Bending over or breaking the tops of onions will result in an earlier harvest but….

At expense of bulb size. The longer onion tops remain green and healthy, the larger the onion. Wait until half the onion tops have fallen over naturally and begun to yellow before harvesting. Gently lift bulbs with a spading fork. Lay out to dry on surface of ground. If rain threatens, move to well-ventilated garage or other dry location.