How to Make It
Heat oil in a large skillet over medium-high. Sprinkle chicken with 1/2 teaspoon salt and 1/4 teaspoon pepper; cook, undisturbed, until browned on one side, 4 to 5 minutes. Stir in orange juice, vinegar, and stock. Turn chicken; cover and cook until chicken is cooked through, about 10 minutes. Transfer chicken to a plate; cover with aluminum foil to keep warm.
Reduce heat to low; cook sauce, stirring occasionally, until reduced to about 1/3 cup, 8 to 10 minutes. Stir in butter until melted; remove from heat, and set aside.
While sauce cooks, prepare couscous according to package directions. Fluff with a fork. Gently stir in pine nuts and chopped scallions.
Fill a saucepan with water, and bring to a boil over high. Add green beans, and cook until tender, 3 to 4 minutes. Using a slotted spoon, transfer beans to a medium bowl. Add orange segments to beans; gently toss. Divide couscous mixture among 4 plates, and add green bean mixture; sprinkle with remaining 1/2 teaspoon salt and remaining 1/4 teaspoon pepper. Top with chicken; drizzle with sauce, and sprinkle with sliced scallions, if desired.