Heat oil in a large skillet or wok over high heat. Add carrots, sweet potato, broccoli, green beans and onion and stir-fry for 5 minutes until vegetables are crisp-tender.
In a small bowl, combine cornstarch, orange juice and soy sauce until smooth. Stir the soy sauce mixture along with the ginger and garlic into the vegetables. Continue to cook and stir for 2 minutes or until sauce has thickened.