Blanch the fava beans in a pot of lightly salted boiling water for 2 minutes and drain. Rinse the beans under cold water to stop the cooking. Peel off and discard the green skins; set aside the beans.
Heat the oil in a large skillet over medium heat. Add the corn, onion, garlic, and salt and cook, stirring frequently, until the vegetables are slightly charred and golden, 6 to 7 minutes. Add the bell pepper and beans and cook an additional 2 minutes. Remove from heat, add the scallion, and toss well. Serve warm or at room temperature.