Preheat oven to 350 degrees. Cut bell peppers into 2-inch-long strips. In a 12-inch heavy skillet heat the oil over moderate heat until hot but not smoking and cook the peppers, stirring frequently, until crisp-tender, about 12 minutes. Transfer cooked peppers to a serving bowl.
In a 4-quart kettle 1/2 filled with boiling salted water cook beans until crisp-tender, about 3 minutes. Drain beans in a colander and transfer to bowl. Toss haricots verts and peppers with salt and pepper to taste.
Adapted from Gourmet Magazine