Heat oven to 350°F. Remove giblets; split hen in half. Rinse and pat dry. Place skin sides up in ungreased 12x8-inch (2-quart) glass baking dish. Arrange carrots around hen.
In 1-quart saucepan, cook jelly, butter, salt and marjoram over low heat 2 to 3 minutes, stirring constantly, until warm. Brush half of sauce over hen and carrots. Cover with foil.
Bake 40 minutes. Uncover; brush with remaining sauce. Add peas; bake 20 minutes longer, brushing with pan juices once or twice, until hen is fork tender, its juices run clear and vegetables are tender.