In a heavy skillet cook the onion, carrots, and garlic in 1 tablespoon of the oil over moderately low heat, stirring, until the carrots are softened and stir in the bell pepper. In a bowl combine the beans, the vegetable mixture, the remaining oil, parsley, lemon juice and salt and pepper to taste. Let stand, covered and chill. The salad may be made 1 day in advance and kept covered and chilled. Serve the salad at room temperature.