Stir the cornstarch, stock and soy sauce in a small bowl until the mixture is smooth.
Spray a 12-inch nonstick skillet with the cooking spray and heat over medium-high heat for 1 minute. Add the chicken and stir-fry until it's well browned, stirring often.
Add the garlic and vegetables and stir-fry for 5 minutes or until the vegetables are tender-crisp.
Stir in the cornstarch mixture and marmalade. Cook and stir until the mixture boils and thickens. Serve over the rice.
