Spray an 8-inch square baking dish with cooking spray and set aside.
In a large skillet, cook beef and onion over medium heat until beef is no longer pink. Drain and return to skillet. Stir in Sloppy Joe sauce and stir over low heat until warmed through.
Pour hot beef mixture into prepared baking dish. Sprinkle with cheese. Arrange biscuit quarters in an even layer on top.
Bake for 15-20 minutes, or until biscuits are cooked through. Let stand for 5 minutes before serving.
Notes
If the tops of your biscuits start to brown and get too dark before the biscuit dough is cooked all of the way through, just cover the dish loosely with foil. Continue baking, covered, until the biscuit dough is cooked through.
To prepare the casserole ahead of time, put the beef mixture into the prepared baking dish, top with cheese, and keep in the refrigerator for up to 24 hours (until ready to bake). To bake, just cover the dish and heat in a 400 degree oven for about 15-20 minutes, or until hot. Then uncover, top with biscuit quarters, and bake for an addition 15-20 minutes.
Can you freeze Sloppy Joe Casserole? Yes! You can freeze the dish before baking (but don't add the biscuits on top until just before you're ready to bake); or you can freeze the casserole after baking. To freeze a baked casserole, allow the dish to cool to room temperature, cover tightly, and freeze for up to 3 months.
To bulk up the filling of your casserole, you can add 1/2 cup of diced green bell pepper to the skillet with the ground beef and onion. Try adding 1 teaspoon of minced fresh garlic, too! Canned or frozen corn kernels would also be a great addition!
Swap out the ground beef and substitute with ground turkey or ground chicken.
To serve a larger family, double all of the ingredients and prepare the casserole in a 9 x 13-inch baking dish. The rest of the cooking instructions remain the same.