Slice beef into very thin strips. Mix cornstarch, broth and soy until smooth. Set aside.
Heat oil in skillet. Add beef and stir-fry until browned and juices evaporate. Push beef to one side of skillet.
Add vegetables and garlic powder and stir-fry until tender-crisp.
Stir cornstarch mixture and add. Cook and stir until mixture boils and thickens. Serve over rice.