Combine oil, vinegar, maple syrup, Dijon, garlic, oregano, about ½ teaspoon salt, and a few grinds of pepper in jar with tight fitting lid: Shake until well combined; set aside.
Bring a large pot of salted water to a boil. Meanwhile, fill a medium bowl with ice water and set aside. Once water is boiling, add cut green beans and boil until just tender, about 2-3 minutes. Drain green beans and immediately transfer to ice bath. Let sit for 2 minutes, then drain. Transfer to a large bowl. (Can be prepared several days in advance and refrigerated until ready to use. You can also substitute frozen green beans, cooking according to package directions and then cooling immediately in ice water.)
Add kidney beans, chickpeas, bell pepper, onion, cucumber, tomatoes, olives, basil, and parsley to the bowl with the green beans. Add dressing and toss well to combine. Serve topped with feta cheese, if desired.