In 3 1/2- to 4-quart slow cooker, combine chicken and simmer sauce; stir gently to mix.
Cover; cook on low setting for 8 to 10 hours or until chicken is no longer pink.
Before serving, stir in thawed vegetables. Increase heat to high setting; cover and cook an additional 15 minutes or until vegetables are crisp-tender. Meanwhile, cook rice in water as directed on package. Serve chicken mixture over rice.