Assemble Ingredients Preheat oven to 425°F. Lightly coat a shallow 2-qt. baking dish with cooking spray. Add mushrooms, broth, soup, rice, and thyme to the prepared dish; stir to combine. Top with butter slices. Cover dish tightly with foil.
Bake Bake 30 minutes. Uncover; top with meatballs. Bake, uncovered, until rice is tender and meatballs are heated through (165°F), about 30 minutes more.
Finish and Serve Top with cheese; tent loosely with foil. Let stand 5 minutes. If you like, sprinkle with additional thyme.
