Mix the cooked and cooled edamame and the two beans in a large mixing bowl.
Add the onions and basil, and stir.
In a small bowl, whisk together the oil, juice, zest, salt and pepper.
Pour the vinaigrette over the bean mixture, and toss well.
Cover and refrigerate until ready to serve. (The salad may be eaten right away, although the flavor will improve slightly after several hours.)
Toss again before serving. Taste for seasoning, adding a little more salt and pepper, according to preference. (Also, the sodium level in different brands of beans varies greatly. Rinsing will remove much of any added salt, but not all.) As an option, garnish with a few thin slices of orange and some basil leaves.