PREHEAT oven to 350°F.
Spray 3-quart oval casserole with nonstick cooking spray.
CUT zucchini lengthwise in half.
Cut crosswise into 1/4-inch-thick slices.
Combine spaghetti sauce, broth, zucchini, mushrooms and rice in prepared dish.
BAKE, covered, 30 minutes.
Remove from oven and stir casserole.
Cover and bake 15 to 20 minutes or until rice is tender.
Remove from oven; sprinkle evenly with cheese.
Bake, uncovered, 5 minutes or until cheese is melted.
Garnish with yellow pepper, if desired.