Microwave Tuna Casserole

This tuna casserole skips the oven entirely and cooks start to finish in the microwave. Broccoli, elbow macaroni, canned tuna, and cream of onion soup come together in one dish, topped with crispy French fried onions that stay crunchy because they go on at the very end.

Cream of onion soup instead of the usual cream of mushroom gives this version a sweeter, more savory base. Mixed with evaporated milk, it creates a rich, creamy sauce that coats every noodle without needing a separate roux.

Brown mustard stirred in adds a sharp, tangy bite that cuts through the creaminess and keeps each spoonful interesting. It’s a small amount but you’d notice if it were missing.

The stirring technique matters in microwave cooking. Pulling food from the outside edges toward the center halfway through equalizes the heat so you don’t end up with a hot ring around a cold middle.

Kitchen Tips

• Defrost and drain the broccoli thoroughly. Excess water from frozen broccoli thins the sauce and makes the casserole soupy.
• Reserve half the fried onions for the topping. Adding them all at the start means they absorb moisture and lose their crunch entirely.
• Add the fried onion topping after the stir, in the last few minutes. This keeps them crispy and golden on top.
• Let the casserole sit for 2 minutes after microwaving. The heat continues to distribute and the sauce thickens slightly as it rests.

Variations

• Cheese addition: Stir in a handful of shredded cheddar with the soup mixture for a cheesier version.
• Peas instead of broccoli: Swap the broccoli for frozen peas for a more classic tuna casserole look.
• Potato chip topping: Crushed potato chips instead of fried onions add a salty, crunchy alternative.