Cook the couscous according to the package directions. Spread on a plate and let cool.
Meanwhile, heat 1 tablespoon of the oil in a large skillet over medium heat. Season the chicken with ¼ teaspoon each salt and black pepper and cook until cooked through, 6 to 8 minutes per side.
Transfer the couscous to a medium bowl and gently toss with the cucumber, cherries, parsley, vinegar, 2 tablespoons of the remaining oil, and ¼ teaspoon each salt and black pepper.
In a small bowl, whisk together the marmalade, orange juice, crushed red pepper, the remaining tablespoon of oil, and ¼ teaspoon salt. Serve the chicken with the couscous salad and drizzle with the marmalade sauce.