Preheat the oven to 350°F. Spray a 9x13-inch baking dish with non-stick cooking spray.
Prepare the rice according to package directions. Set aside.
Bring a small pot of water to a boil. Add the broccoli and cook for 2 minutes, until bright green in color. Drain and set aside.
In a large, deep skillet over medium-high heat, melt the butter. Add the mushrooms and onion. Cook, stirring frequently for 3 minutes, until softened. Turn off the heat.
Into the skillet, add the rice, broccoli, stuffing mix, and chicken-style broth. Stir to combine.
Transfer the skillet mixture to the baking dish. Bake, uncovered, for 30 minutes, until heated through and golden. Serve warm or room temperature.