Preheat oven to 350°F. Spray a 9x13 baking dish with nonstick cooking spray.
In a medium skillet on medium-high heat, brown the lean ground beef for 5 to 7 minutes or until no pink remains. Drain off the excess fat that was rendered from cooking.
To a large mixing bowl, add the browned and drained lean ground beef, packet of beefy onion soup mix, cream of mushroom soup, sliced mushrooms, beef broth, whole milk, sour cream, salt, and black pepper. Stir to combine.
Stir in the minute rice and spread the mixture into the prepared baking dish.
Top the hamburger rice casserole with the shredded Colby jack cheese.
Tightly cover the casserole dish with a large piece of aluminum foil.
Bake for 45 minutes. Uncover the hamburger rice casserole and place it under the broiler for 2 to 3 minutes or just until the cheese is lightly browned and bubbly. Be sure to keep a close eye on the cheese so that it doesn’t burn while under the broiler.
Allow the hamburger rice casserole to cool for 5 minutes before garnishing with fresh chopped parsley and serving.
You can cook a large batch of ground beef ahead of time and store it in one-pound portions in the freezer for up to two months. Thaw the cooked ground beef in the refrigerator for 6 to 12 hours before using it in quick weeknight meal preparations like this hamburger casserole with rice.
To keep your cheese from sticking to the aluminum foil while your casserole bakes, lightly spray the aluminum foil (the side facing the cheese) with nonstick cooking spray before covering your baking dish.
Oven temperatures vary and may need to be recalibrated periodically to ensure they are accurate. Make sure to keep a close eye on your casserole as the suggested cook time approaches.