Place the rice in a fine- mesh sieve and rinse under cold running water for about 30 seconds. Bring a large pot of water to boil. Add the rice and boil (like pasta) until tender, 40 to 45 minutes, then remove the rice from the heat. Drain the rice and return it to the pot. Cover and allow it to steam for 10 minutes. Uncover the pot and fluff the rice gently with a fork. Re-cover and set aside.
While the rice cooks, fill another pot with a few inches of water and fit it with a steamer insert. Bring the water to a simmer. Add the broccoli and edamame to the steamer insert. Steam for 5 minutes, or until the broccoli is tender, yet still bright green and crisp, and the edamame is warm.
Place the rice, broccoli, edamame, and cabbage into a large mixing bowl. Add the vinaigrette and mix well to combine.
Divide the grain salad into plates or onto bowls. Garnish each plate with some orange section and a sprinkling of chopped scallion tops, if you like. Serve.
Notes
The grain salad can be dressed and stored in an airtight container in the fridge for up to four days. Add the oranges and scallion tops right before serving.