Recipe for Insalata di Tonno e Fagioli

1 lg. can of canneloni beans
1 lg. onion-sliced
1/2 lb. of fresh green beans-cleaned, and boiled or steamed
1/3 cup of olive oil
2 tsp. vinegar
salt, and pepper
1 7oz. can of tuna in oil-drained

Mix all the ingredients together, and chill.