Cook rice in water as directed on package, omitting salt.
Meanwhile, in small bowl, mix orange juice concentrate, soy sauce, cornstarch and garlic powder until smooth.
Heat 10-inch nonstick skillet over medium-high heat. Add chicken; cook 5 to 8 minutes, stirring frequently, until chicken is no longer pink in center.
Stir in juice concentrate mixture and vegetables. Reduce heat to medium; cover and cook 6 to 8 minutes, stirring occasionally, until vegetables are crisp-tender. Serve over rice. Garnish with onions.