Baked Seafood Casserole: A Creamy, Comforting Dinner Straight From the Oven

There is something especially satisfying about a seafood casserole. It combines tender seafood, a rich and flavorful sauce, and a golden topping into one bubbling dish that feels both comforting and elegant. Baked Seafood Casserole is an excellent choice when you want a dinner that looks impressive without requiring complicated cooking techniques.

This version brings together shrimp, white fish, and scallops with a creamy garlic-herb sauce, vegetables, and a crisp Parmesan breadcrumb topping. The seafood stays tender while the casserole develops a beautifully browned surface in the oven.

What Makes This Seafood Casserole Special?

The secret is in the balance. Seafood can become dry or rubbery if it is overcooked, so the casserole is assembled with ingredients that help protect its delicate texture.

A lightly seasoned cream sauce gives the dish richness, while lemon adds brightness. A mixture of Parmesan cheese and breadcrumbs creates a crunchy contrast against the creamy seafood underneath.

You can also adapt the recipe depending on what is available. Crab meat, lobster, mussels, or firm pieces of salmon can all work well.

Ingredients

For the Seafood

• 1 pound large shrimp, peeled, deveined, and halved if large
• 8 ounces firm white fish, such as cod or haddock, cut into bite-sized pieces
• 6 ounces sea scallops, patted very dry
• 1 tablespoon olive oil
• ½ teaspoon salt
• ¼ teaspoon black pepper
• ½ teaspoon paprika
• ½ teaspoon garlic powder

For the Creamy Sauce

• 2 tablespoons butter
• 3 cloves garlic, finely minced
• ½ small onion, finely diced
• 2 tablespoons all-purpose flour
• 1 cup whole milk
• ½ cup heavy cream
• ½ cup low-sodium chicken or vegetable broth
• ½ cup grated Parmesan cheese
• 1 tablespoon fresh lemon juice
• 1 teaspoon Dijon mustard
• ½ teaspoon dried Italian herbs
• 2 tablespoons chopped fresh parsley

For the Vegetable Layer

• 1 cup sliced mushrooms
• 1 cup baby spinach
• ½ cup finely chopped bell pepper

For the Topping

• ½ cup panko breadcrumbs
• ¼ cup grated Parmesan cheese
• 1 tablespoon melted butter
• 1 tablespoon chopped parsley

Equipment

You will need:

• A large skillet
• A 9×13-inch baking dish
• A mixing bowl
• A whisk
• A cutting board and knife

Step-by-Step Method

Step 1: Prepare the Seafood

Begin by patting the shrimp, fish, and scallops thoroughly dry with paper towels.

This simple step makes a noticeable difference. Excess moisture can cause the seafood to release too much liquid while baking, resulting in a watery casserole.

Place the seafood in a bowl and season it with salt, black pepper, paprika, and garlic powder. Toss gently so the seasoning coats each piece.

Step 2: Give the Seafood a Quick Sear

Heat the olive oil in a large skillet over medium-high heat.

Add the shrimp and cook for approximately 1 minute per side, just until they begin to turn pink. Remove them from the skillet.

Add the scallops and sear them briefly, about 1 minute per side, then remove them as well.

The seafood does not need to be fully cooked at this stage. It will finish cooking in the oven.

Add the seasoned fish to the same skillet and cook for about 1–2 minutes, turning gently. Remove it from the heat.

This quick searing step adds flavor while preventing the seafood from spending too long in the oven.

Step 3: Sauté the Vegetables

Using the same skillet, add the butter.

Once melted, add the diced onion, mushrooms, and bell pepper. Cook for approximately 4–5 minutes, stirring occasionally.

When the vegetables have softened, add the minced garlic and cook for another 30 seconds.

Finally, stir in the spinach and cook until it has just wilted.

Step 4: Make the Cream Sauce

Sprinkle the flour over the vegetables and stir continuously for about 1 minute.

Gradually pour in the milk while whisking. This helps prevent lumps from forming.

Add the heavy cream and broth, continuing to whisk until everything is smooth.

Stir in:

• Parmesan cheese
• Dijon mustard
• Italian herbs
• Lemon juice
• Fresh parsley

Allow the sauce to simmer gently for approximately 3–5 minutes, stirring frequently.

It should become creamy enough to lightly coat the back of a spoon.

Taste and adjust the seasoning if needed.

Step 5: Combine the Seafood and Sauce

Preheat your oven to 375°F (190°C).

Lightly grease a 9×13-inch baking dish.

Spread a small amount of the creamy sauce across the bottom of the dish. Arrange the partially cooked shrimp, fish, and scallops over the sauce.

Pour the remaining sauce evenly over the seafood.

Avoid stirring everything aggressively because the fish and scallops can break apart.

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