Preheat the broiler. Place the red peppers on a foil lined baking sheet.
Place the red peppers under the boiler. Turning every 2 to 3 minutes cook the peppers until the skin is blistered, about 8 to 9 minutes total. Place the blistered peppers in a plastic bag. Seal the bag and allow the peppers to sit for 10 minutes to allow the skin to separate and to let cool.
Meanwhile, bring a large pot of salted water to a boil over high heat. Add the potatoes and cook until tender, about 10 to 12 minutes. Remove the potatoes to a cutting board. Add the green beans to the pot. Cook the green beans until tender, about 3 minutes. Remove the green beans to a large bowl. Slice the potatoes in half while still warm and combine them with the green beans in the large bowl. Remove the peppers from the plastic bag. Peel off the skin from the peppers. Slice the pepper flesh into wide strips and remove the seeds and veins. Place them in the bowl with the potatoes. Add the scallions, parsley, and garlic
and toss to combine.
In a small bowl combine the oregano, lemon juice and zest, and white wine vinegar. Whisk in the olive oil. Stir in the salt and pepper. Toss the warm vegetables with the herb vinaigrette. Serve immediately.