Easy Seafood Casserole Recipe

I never thought a seafood casserole could be simple until my neighbor shared this recipe with me. Growing up, my mom only made casseroles with canned tuna, and they were always a bit dry and boring. When I tried making fancier seafood dishes, they usually ended up overcooked or just not quite right.

That’s because I was making things too complicated—trying to cook everything separately and using too many ingredients. This seafood casserole, though, is different.

It’s straightforward, comes together in one dish, and even my kids, who usually turn their noses up at seafood, ask for seconds. For busy parents who want to get dinner on the table without any fuss, this recipe is a game-changer.

What Kind of Seafood Should I Use?

This recipe is pretty flexible when it comes to the seafood you choose to include. While the recipe calls for flounder, you can easily swap it for any mild white fish like cod, haddock, or sole – just make sure the fillets are about the same thickness so they cook evenly.

For the shrimp, medium or large sizes work well (21-25 or 16-20 count per pound), and you’ll want them peeled and deveined to make eating easier.

When it comes to scallops, go for “dry” sea scallops rather than “wet” ones that have been treated with preservatives – they’ll give you better browning and a sweeter flavor.

For the crabmeat, while lump is specified, you could also use jumbo lump for a more luxurious dish, or even backfin if you’re watching your budget.

Options for Substitutions

This seafood casserole is pretty flexible and you can make several swaps while keeping it tasty:

• Flounder fillets: Any mild white fish works great here – try cod, haddock, or sole. Just make sure it’s not too thick, or you might need to adjust the cooking time a bit.
• Shrimp and scallops: You can use all shrimp or all scallops if you prefer. If using smaller shrimp, just add a few more to make up the amount. Frozen seafood is totally fine – just thaw it completely first.
• Lump crabmeat: While real crab meat gives the best flavor, imitation crab can work if you’re on a budget. You could also skip it and add extra shrimp or scallops instead.
• Heavy cream: Half-and-half can work, but the sauce won’t be as rich. If using half-and-half, you might need to thicken the sauce with 1 teaspoon of cornstarch mixed with cold water.
• Chicken stock: Fish stock or clam juice make great substitutes and add extra seafood flavor. In a pinch, vegetable stock works too.
• Old Bay seasoning: If you don’t have Old Bay, mix together a pinch each of celery salt, paprika, and cayenne pepper for a similar flavor profile.

Watch Out for These Mistakes While Cooking

The biggest challenge when cooking seafood casserole is overcooking the delicate proteins – shrimp and scallops only need 3-4 minutes to cook through, while fish fillets should be just opaque in the center.

To prevent a watery casserole, make sure to pat all seafood completely dry with paper towels before cooking, and avoid overcrowding the pan which can cause the seafood to steam rather than properly brown.

The cream sauce can break if heated too quickly or at too high a temperature, so keep your heat at medium-low and stir constantly while incorporating the cream into the chicken stock.

For the best flavor development, season each type of seafood separately before combining, and remember to let the casserole rest for 5 minutes after baking – this allows the sauce to thicken and the flavors to settle together perfectly.

What to Serve With Seafood Casserole?

This rich seafood casserole pairs perfectly with simple sides that won’t overshadow its delicate flavors.

A side of plain white rice or angel hair pasta makes an excellent base to soak up all that creamy sauce.

For vegetables, steamed asparagus or roasted broccoli work really well – just add a squeeze of lemon to brighten things up.

If you want to keep it light, a simple mixed green salad dressed with a basic vinaigrette lets the casserole remain the star of the show.

Storage Instructions

Keep Fresh: This seafood casserole will stay good in the fridge for up to 2 days when stored in an airtight container. Since it contains various types of seafood, it’s best to enjoy it sooner rather than later to maintain the best taste and texture of the shrimp, scallops, and fish.

Freeze: While you can freeze this casserole, I wouldn’t recommend it as seafood can become rubbery when frozen and reheated. The cream sauce might also separate during the thawing process, affecting the overall quality of the dish.

Warm Up: To reheat leftovers, place them in a covered dish in a 325°F oven for about 15-20 minutes, or until heated through. You can add a splash of cream if the sauce seems too thick. Avoid using the microwave as it can make the seafood tough and chewy.

Seafood Casserole FAQ

Why is my seafood casserole sauce too thin?

The key to getting the right sauce consistency is letting it simmer and reduce properly.

I always make sure to let my cream sauce bubble gently for about 5-7 minutes before adding the seafood.

If your sauce is still too thin, you can continue simmering it for a few more minutes until it coats the back of a spoon.

Should I thaw frozen seafood before adding it to the casserole?

Yes, you should always thaw frozen seafood before using it in this casserole. I place my frozen seafood in the refrigerator overnight or use the cold water method (placing sealed seafood in cold water for about 30 minutes).

Using thawed seafood ensures even cooking and prevents excess water from making your sauce runny.

Can I prepare the sauce while the seafood is cooking?

No, I recommend making the cream sauce first, then adding the seafood. The sauce needs time to develop its flavors and reach the right consistency, and seafood cooks very quickly.

If you cook the seafood first or at the same time, it might become overcooked and rubbery while you’re waiting for the sauce to thicken.

Preparation Time	15-25 minutes
Cooking Time	35-45 minutes
Total Time	50-70 minutes
Level of Difficulty	Medium

Ingredients

• 4 ounces flounder fillets (divided into two parts)
• 6 extra-large shrimp
• 6 large scallops
• 4 ounces lump crabmeat
• 4 tablespoons butter
• 1/2 cup heavy cream
• 3/4 cup chicken stock
• 1 tablespoon dijon mustard
• 1/2 teaspoon garlic powder
• 1/2 teaspoon onion powder
• 1/4 teaspoon black pepper
• 1/2 teaspoon old bay seasoning (optional)
• 1/2 teaspoon chopped italian parsley (optional)

Step 1: Sauté the Seafood

In a large skillet over medium-high heat, melt two tablespoons of butter.

If you prefer, you can substitute olive oil for the butter.

Once hot, add the shrimp and scallops to the pan.

Sauté these for about a minute, just long enough to sear the outside.

Add a splash of white wine to deglaze the pan, then incorporate the heavy cream, chicken broth, dijon mustard, and your chosen seasonings.

Continue sautéing the mixture for an additional minute before removing the shrimp and scallops from the pan.

Set them aside for later use.

Step 2: Create and Thicken the Sauce

To the pan with the remaining seafood sauce, add two tablespoons of butter that have been dredged in flour (also known as beurre manie).

This will act as a thickening agent.

Let the mixture simmer over low heat until the sauce has thickened to your desired consistency.

Once thickened, remove the pan from heat and mix the seared scallops, shrimp, and crab meat into the sauce, ensuring all the seafood is well-coated.

Set aside this seafood mixture for later use.

Step 3: Prepare and Bake the Flounder

Preheat your oven to 350° F.

Place the flounder fillets at the bottom of each casserole dish.

Add a little water to the dish, then sprinkle the fillets with Old Bay seasoning.

Bake the flounder in the preheated oven for 10 minutes.

After baking, drain any excess water from the casserole dish.

Step 4: Assemble and Final Bake

With the flounder pre-baked and the water drained off, add the prepared seafood mixture on top of the flounder fillets in the casserole dish.

Sprinkle with additional Old Bay seasoning for extra flavor.

Return the casserole dish to the oven and bake at 350° F for an additional 25 minutes, or until the top becomes golden brown and bubbly.

Step 5: Serve and Enjoy

After baking, remove the casserole dish from the oven and let it cool slightly before serving.

Enjoy your flavorful and perfectly baked seafood casserole!