Preheat oven to 300 F.
Add broth, lentils, brown rice, chopped onion, and spices to 9x13-inch glass baking dish. Stir together and cover tightly with foil.
Bake at 300 F for 1 hour and 10 minutes.
Remove foil and sprinkle shredded cheese over the top and return to oven and bake uncovered for 20 more minutes, or until cheese is completely melted.
Steam broccoli in stovetop steamer or in a microwavable dish covered with plastic wrap for 4-5 mintues.
Serve Lentil and Brown Rice Casserole with Steamed Broccoli.