Thinly slice the onions. Discard the tops from the fennel, then core and thinly slice the bulb. Drain and thinly slice the roasted peppers. Rinse and drain the chick-peas.
Heat the oil in a large saucepan over medium heat. Add the onions and sauté, stirring occasionally, until tender and somewhat golden, about 5 minutes. Add the vinegar and continue to sauté un