Easy Low-Carb Ground Beef Casserole

There’s something comforting about the sound of ground beef sizzling in a hot skillet, especially once garlic and onion hit the pan. Add bubbling cheese on top, and suddenly a simple weeknight dinner feels like something everyone actually wants to sit down for.

This Easy Low-Carb Ground Beef Casserole combines seasoned beef, zucchini, spinach, tomato sauce, and plenty of melted cheese without pasta, rice, or potatoes. It’s hearty enough for dinner but simple enough for a busy night.

The key is cooking the zucchini until its extra moisture evaporates before the casserole goes into the oven. That small step keeps the filling rich and creamy instead of watery.

Why You’ll Love This Recipe

• Quick: Ready in about 40 minutes.
• Low-carb: Packed with beef, zucchini, spinach, and peppers.
• Easy cleanup: Most of the cooking happens in one skillet.
• Meal-prep friendly: Reheats well for easy lunches or dinners.
• Family-friendly: Cheesy, creamy, and mildly seasoned.

Ingredients

• 1 1/4 lb lean ground beef (567 g)
• 1 Tbsp olive oil (14 g)
• 1 small yellow onion, diced (110 g)
• 1 medium red bell pepper, diced (150 g)
• 2 medium zucchini, diced (260 g)
• 3 garlic cloves, minced (9 g)
• 2 Tbsp tomato paste (32 g)
• 3/4 cup no-sugar-added marinara sauce (185 g)
• 3 cups baby spinach (90 g)
• 3 oz cream cheese, softened (85 g)
• 1 cup shredded sharp cheddar cheese (113 g)
• 1/2 cup shredded low-moisture mozzarella cheese (56 g)
• 2 tsp Italian seasoning (4 g)
• 1 tsp smoked paprika (2 g)
• 1 tsp kosher salt (6 g), divided
• 1/2 tsp ground black pepper (1 g)
• 1/4 tsp crushed red pepper flakes (0.5 g), optional

How to Make This Recipe

Step 1: Brown the Beef

Preheat the oven to 400°F (204°C) and lightly grease a 9-by-13-inch baking dish. Heat a large skillet over medium-high heat, then add the ground beef. Season with half the salt and black pepper and cook for 6–8 minutes, breaking it into small crumbles. Let some pieces sit untouched for 30–60 seconds so they develop browned edges instead of simply steaming. Pro Tip: Drain excess grease if your beef releases more than a tablespoon or two.

Step 2: Cook the Vegetables

Add the olive oil if needed, followed by the onion, bell pepper, and zucchini. Cook uncovered for 6–8 minutes, stirring occasionally, until the onion softens and the zucchini releases most of its moisture. Next, stir in the garlic, tomato paste, Italian seasoning, smoked paprika, red pepper flakes, and remaining salt. Cook for another minute, until the tomato paste darkens slightly and the garlic smells fragrant. Pro Tip: If you still see liquid pooling in the skillet, cook another 2 minutes before continuing.

Step 3: Make the Creamy Filling

Stir the marinara and spinach into the skillet. Cook for 2–3 minutes, just until the spinach wilts and the sauce begins to simmer. Reduce the heat to low, then stir in the softened cream cheese until it melts into the beef mixture. The filling should look thick and creamy, not soupy. Avoid the common mistake of adding the cream cheese while the pan is fiercely boiling; gentle heat helps it blend more smoothly.

Step 4: Add Cheese and Bake

Spread the beef mixture evenly in the prepared baking dish, then scatter the cheddar and mozzarella over the top. Bake uncovered for 12–15 minutes, until the edges bubble and the cheese is fully melted. For deeper browning, broil for 1–2 minutes, watching closely. Pro Tip: Rest the casserole for 5–10 minutes before serving. I learned this one the messy way—cutting it immediately gives you a plateful of runaway sauce instead of neat portions.

Expert Tips for Perfect Results

• Cook the zucchini uncovered. High-moisture vegetables can make a zucchini casserole watery if they’re only partially cooked before baking. Giving that moisture somewhere to escape makes a noticeable difference.
• Use a wide skillet. Crowding ground beef causes it to release steam faster than it can brown. More surface area gives you those savory browned bits that add extra flavor.
• Soften the cream cheese first. Let it sit at room temperature while you prep the vegetables. It blends much faster and leaves fewer little white lumps.
• Grate your own cheese when convenient. Freshly grated cheese usually gives this cheesy ground beef casserole a smoother melted topping.
• Don’t skip the resting time. Five minutes lets the hot sauce settle around the beef and vegetables, so portions hold together better.

Variations

• Make it more keto-friendly by skipping the bell pepper and adding 1 cup (90 g) sliced mushrooms or extra spinach. Choose a marinara that fits your preferred carbohydrate target.
• Turn it spicy with one diced jalapeño, an extra 1/4 tsp red pepper flakes, and pepper Jack cheese in place of mozzarella. This works especially well if your family likes taco-style heat.
• Swap the beef for 1 1/4 lb (567 g) ground turkey for a lighter-tasting version. Very lean turkey may need an extra 1 tsp olive oil during browning.
• Make it dairy-free with unsweetened dairy-free cream cheese and a dairy-free shredded cheese that melts well. The texture will vary by brand, so keep the filling slightly thicker before baking.
• Add more vegetables by replacing about one-quarter of the beef with browned mushrooms or chopped cauliflower. Cook either one first so excess water doesn’t dilute the sauce.

Serving Suggestions

• Serve with a simple arugula or romaine salad and lemon vinaigrette; the crisp acidity balances the creamy beef and cheese.
• Top each portion with chopped parsley, basil, or sliced green onions for fresh color and a lighter finish.
• Add a spoonful of sour cream or plain Greek yogurt plus sliced jalapeños if you like a cool, tangy topping.
• Pair this family-friendly dinner with roasted broccoli, garlic green beans, or mashed cauliflower to keep the entire meal lower in carbs.
• Serve sparkling water with lime, unsweetened iced tea, or a light red wine alongside the casserole to balance its richer flavors.

Storage & Reheating

Let the casserole cool, then transfer leftovers to shallow airtight containers. Refrigerate for 3–4 days. Ground-beef casseroles are also commonly frozen in individual portions for easier reheating.

For the best quality, freeze portions for up to 2–3 months. Because cream cheese can become slightly grainier after freezing, thaw the casserole overnight in the refrigerator and reheat it gently rather than using very high heat.

Reheat larger portions covered in a 350°F (177°C) oven for about 15–20 minutes, or until hot through the center. Individual servings can be microwaved for 1–2 minutes, then continued in 30-second bursts as needed.