French Onion Stuffed Meatballs

Stuffed with caramelized onions and mozzarella, these French onion meatballs are inspired by the classic onion soup recipe. I cover the homemade meatballs with more cheese and broil them until golden brown and bubbly. Yes, you can even make these French onion meatballs gluten-free!

Every winter, my dad would make grilled cheese and French onion soup. I eagerly awaited those crocks of soup, with those rich, caramelized onions, beefy broth, and heaps of melty cheese. Now that I’m cooking for my own family, I’ve found more ways to make those flavors into dinner, from French onion meatloaf and French onion burgers to today’s French onion meatballs.

My dad’s version of French onion soup, which inspired this easy meatball recipe, uses mozzarella instead of the traditional Gruyère cheese. So naturally, that’s what I stuffed into the meatballs! They’re drenched in a rich, beefy sauce and baked until the cheese inside becomes a pocket of melty deliciousness surrounding the caramelized onions.

Why These French Onion Meatballs Are My Favorite

• A classic, remade. These French onion meatballs are stuffed with cheese and onions and smothered in a simple, rich sauce made of beef stock and red wine. The flavors are just like French onion soup!
• Don’t forget the au gratin. The entire pan gets covered with more mozzarella and placed under the broiler to get that perfectly browned cap of toasty cheese.
• Easily made gluten-free. Yes, you can use gluten-free breadcrumbs or even slightly ground oats to bind the meatballs together.

How to Make French Onion Meatballs

You’ll need a nice, large skillet that is safe to put in the oven and under the broiler. I’ve included alternatives in my tips below! Once you have this plus your ingredients at the ready, here’s how to make the most amazing French onion meatballs:

• Caramelize the onions. Begin by sautéing the onions in olive oil until they’re golden and caramelized. Add the thyme, wine, and beef broth, and reduce until very little liquid remains. 
• Make the meatballs. Combine the raw meatball ingredients in a bowl. I use my hands to work everything together – but not too much, or the meatballs will turn out dense. Next, divide the mixture into even-sized balls.

Variation Ideas

• Make chicken or turkey stuffed meatballs: Trade out the ground beef for leaner meats like ground chicken or ground turkey (ground pork is also an option). 
• Different cheeses: Instead of mozzarella, try stuffing your French onion meatballs with other cheese varieties like cheddar, ricotta, Monterey Jack, or even Gruyere cheese.
• Switch up the sauce: You can bake these meatballs in other savory sauces, like tomato sauce, vodka sauce, or a homemade marinara sauce.
• Add extras: In addition to caramelized onions and thyme, you can add other ingredients to the meatball filling, like mushroom duxelles (from my Beef Wellington recipe), as well as different herbs like fresh chopped basil and rosemary. 

Tips for Perfect Meatballs

• Don’t rush. It’s important to caramelize the onions slowly, so that they develop the deep caramelized color and flavor without burning. Be sure to stir frequently and reduce the heat if necessary.
• Use the right wine. Most red wines will work well for this recipe. It doesn’t need to be an expensive bottle, but I would recommend using a wine you would drink (versus cooking wine).
• Use an oven-safe skillet (or an alternative). I like using my 10-inch cast iron skillet as it browns the meatballs nicely and it’s oven (and broiler) safe. If you do not have an oven-safe skillet, transfer the meatballs to a casserole dish before adding the sauce and baking them in the oven.
• Portion the meatballs with a cookie scoop. If you want to ensure your meatballs are evenly sized, this is a great option for portioning out the mixture.

Can I Make These in Advance?

One of the best parts about this recipe? If you have the time, you can make loads of these delicious onion and mozzarella stuffed meatballs. They’re the perfect recipe to prepare in advance, for later baking or freezing. You can even freeze the meatballs raw (just as long as you’re working with meat that was fresh and not frozen to begin with).

Storing and Reheating Leftovers

• Fridge. Store leftover meatballs in an airtight container in the fridge for up to 3-4 days.
• Freezer. These stuffed meatballs freeze really well! Place the cooked or uncooked meatballs in a single layer on a baking sheet to pre-freeze. Once they’re solid, transfer them to freezer bags to keep frozen for up to 3-4 months. Let the meatballs thaw in the fridge before browning and/or baking them in the sauce.
• Reheat. Gently reheat the meatballs in the oven or microwave, or even in a skillet on the stove. You may want to give them a fresh sprinkle of cheese once they’re warm to revive the topping a bit.

Make It a Meal

Savory, saucy French onion meatballs are wonderful to serve over egg noodles, rice, or even spaghetti squash alongside a fresh garden salad with creamy balsamic dressing. Here are some more serving suggestions:

• Make some mashers. Spoon your meatballs over a base of Instant Pot Mashed Potatoes, or pair these meatballs with cheesy scalloped potatoes or restaurant-worthy air fryer truffle fries.
• Veggies: Add a side of air fryer Brussels sprouts, balsamic roasted vegetables, or creamed spinach.
• Bread: Bake a loaf of gluten-free French bread to slice and scoop up that decadent sauce!

More Meatball Recipes

• Barbecue Baked Turkey Meatballs
• Gluten Free Italian Meatballs
• Porcupine Meatballs
• General Tso’s Chicken Meatballs
• Teriyaki Turkey Meatballs