Heat oil in large skillet or wok over medium-high heat until hot. Add chicken; cook and stir 3 to 5 minutes or until browned.
Add carrots, celery, bell pepper, onion, broth, soy sauce, sugar, garlic powder and gingerroot; mix well. Bring to a boil. Reduce heat to low; simmer 5 minutes or until vegetables are crisp-tender and chicken is no longer pink. Stir in bean sprouts; cook an additional 2 to 4 minutes or until thoroughly heated.
In small bowl, combine cornstarch and water; blend well. Gradually stir into mixture in skillet. Cook and stir over medium heat until sauce is bubbly and thickened. Sprinkle with chow mein noodles.