Cook the sausage in a 12-inch skillet over medium-high heat until it's well browned, stirring often to separate meat. Pour off any fat.
Add the mushrooms, celery, pepper, onion, thyme, marjoram and seasoning packet from the rice blend to the skillet and cook until the vegetables are tender-crisp.
Stir the sausage mixture, stock, soup, rice blend and 1/2 cup cheese in a 3-quart shallow baking dish. Cover the baking dish.
Bake at 375 degrees F for 1 hour or until the sausage is cooked through and the rice is tender. Stir the sausage mixture before serving. Sprinkle with the remaining cheese.
Tip: For an extra-special touch, substitute 1 package (8 ounces) baby portobello mushrooms, sliced, for the sliced mushrooms.