This 4 ingredient low carb cheesy casserole using canned tuna is the kind of cozy, no-fuss dinner that fits right into a busy weeknight. It comes together in the same glass baking dish you serve it in: you just toss drained canned tuna with three simple pantry staples—mayonnaise, shredded cheese, and a sprinkle of dried seasoning—then bake until it’s bubbly and golden. It’s budget-friendly, kid-pleasing, and has that creamy, cheesy comfort that makes everyone at the table go back for seconds.
Serve this casserole hot right from the oven with a bright, crunchy side to balance the creamy richness. A simple green salad with a tangy vinaigrette, sliced cucumbers and cherry tomatoes, or steamed broccoli all work beautifully. If you’re not strictly low carb, you can add a basket of buttered toast or garlic bread for dipping into the cheesy edges. A bowl of tomato soup on the side also turns this into a cozy, diner-style meal that feels extra comforting on chilly nights.
4 Ingredient Low Carb Cheesy Tuna CasseroleServings: 4
Ingredients
3 (5-ounce) cans tuna in water, well drained
1 cup mayonnaise
2 cups shredded mild cheese (such as mozzarella or Monterey Jack), divided
1 teaspoon dried Italian seasoning or mixed dried herbs
Cooking spray or a little butter for greasing the dish (optional, for the pan)
Directions
Preheat your oven to 375°F (190°C). Lightly grease a 2-quart glass baking dish with cooking spray or a little butter so the casserole doesn’t stick.
Open the cans of tuna and drain them very well, pressing the lids gently to squeeze out excess liquid. This helps keep the casserole from getting watery.
Scatter the drained tuna evenly across the bottom of the glass baking dish, breaking up any large chunks with a fork but leaving some texture. You want a fairly even layer of tuna covering the bottom.
In a medium bowl, stir together the mayonnaise, 1 1/2 cups of the shredded cheese, and the dried Italian seasoning until you have a thick, creamy mixture.
Spoon the cheesy mixture over the tuna in the baking dish, then use the back of the spoon to spread it out so it completely covers the tuna. It’s fine if some tuna peeks through in spots, but aim for a generous blanket of the creamy mixture.
Sprinkle the remaining 1/2 cup shredded cheese evenly over the top, creating a thick, pale layer of cheese that covers most of the surface. This is what will melt into that irresistible cheesy crust.
Place the glass baking dish on the middle rack of the preheated oven and bake for 18–22 minutes, or until the casserole is bubbling around the edges and the cheese on top is melted and just starting to turn golden in spots.
Remove the casserole from the oven and let it rest for about 5 minutes. This short rest helps it set up a bit so it scoops nicely. Serve warm, straight from the baking dish, and watch it disappear.
Variations & Tips
For families, this casserole is easy to tweak for different tastes. If you have kids who are picky about herbs, you can swap the Italian seasoning for just a pinch of garlic powder and a little salt and pepper. For extra creaminess, stir 2–3 tablespoons of softened cream cheese into the mayonnaise mixture. If you’d like more vegetables without adding carbs, fold in a handful of finely chopped cooked broccoli, spinach, or cauliflower rice with the tuna before topping with the cheese mixture. To make it a bit more filling while still staying relatively low carb, you can sprinkle cooked, crumbled bacon over the top before baking. For a slightly sharper flavor, use a blend of mild mozzarella and a little shredded cheddar or Swiss. If you need this recipe to be gluten-free, simply check that your canned tuna and dried seasoning blend are certified gluten-free; the base recipe itself doesn’t use flour or breadcrumbs. Food safety tips: always drain the tuna thoroughly and keep it refrigerated until you’re ready to assemble. Once baked, refrigerate leftovers within 2 hours in a covered container and eat within 3–4 days, reheating only the portion you plan to serve. Reheat in a 300°F (150°C) oven until hot in the center, or gently in the microwave, making sure it reaches a steaming temperature before serving.
