This Spinach Stuffed Flounder is one of those weeknight-to-weekend recipes I keep in heavy rotation. It’s straightforward to assemble, bakes in a single dish, and delivers a tender, flaky fish with a creamy, savory filling. No tricky techniques — just clean flavors and a pleasing presentation that feels like effort without demanding an afternoon.

Start to finish this takes under an hour and mostly waits while the oven does its job. The filling is a mix of cream cheese, mozzarella, feta, and baby spinach: rich enough to satisfy, bright enough from the feta and spinach to keep the dish from feeling heavy. I like serving it with a simple grain or quick salad and a lemon wedge.

Below you’ll find the exact ingredient list and step-by-step directions I use at home, plus practical tips for success, equipment suggestions, storage guidance, and answers to common questions. Read the steps through once before beginning, then follow the sequence and you’ll have a dinner that looks nicer than it takes to make.

Ingredient Rundown

6 flounder fillets, about 4–6 oz each, boneless & skinless — These are the base; similar-sized fillets roll more evenly.
½ tsp. Old Bay Seasoning or to taste — A little seasoning goes a long way; sprinkle evenly for balanced flavor.
1 tbsp. olive oil — For a light brush on top to encourage even browning.
3 oz. cream cheese, softened — Binds the filling and keeps it creamy; soften to room temperature for easy mixing.
½ cup mozzarella cheese, shredded — Adds stretch and melt; use freshly shredded for best texture.
½ cup feta cheese, crumbled — Brings tang and saltiness; distribute evenly in the filling.
3 oz. baby spinach, roughly chopped — Adds color, freshness, and a vegetal lift; squeeze out excess moisture if very wet.

From Start to Finish: Spinach Stuffed Flounder

Preheat the oven to 350°F and place a rack in the center of the oven.
In a large mixing bowl combine 3 oz softened cream cheese, ½ cup shredded mozzarella, ½ cup crumbled feta, and 3 oz roughly chopped baby spinach. Mix with a spoon or your hands until well combined and spreadable.
Pat the 6 flounder fillets dry with paper towels. Sprinkle the ½ tsp Old Bay Seasoning evenly over the fillets.
Divide the cheese-and-spinach mixture into 6 equal portions.
Working one fillet at a time, place one portion of filling near the tail end of the fillet. Starting at the tail, roll the fillet up jelly-roll style and place it seam side down in a baking dish. Repeat with the remaining fillets and filling.
Using the 1 tbsp olive oil, brush the tops of the rolled fillets lightly with oil.
Bake the stuffed flounder at 350°F for about 20 minutes, until the fish is cooked through and flakes easily with a fork.
Remove from the oven and let rest 2–3 minutes before serving.

Why This Recipe Belongs in Your Rotation

It’s quick. Prep is mostly assembly, and the oven does the rest. That makes it ideal for busy weeknights when you want something better than takeout without fuss. It also scales well for a dinner party — the rolled fillets plate nicely and look composed.

The flavor profile is dependable. Cream cheese and mozzarella give the filling a velvety texture, while feta keeps things lively with tang. Old Bay adds subtle warmth and a coastal vibe that complements the mild flounder without overpowering it. Spinach adds freshness and a color contrast that makes each piece inviting.

Low-Carb/Keto Alternatives

This recipe is already quite friendly to low-carb and keto menus, since it’s centered on fish, cheese, and greens. A couple of small changes tune it for stricter carb limits or to tighten the macros:

Serve with low-carb sides: Swap grains or potatoes for roasted cauliflower, a quick sautéed green like garlic spinach, or a creamy cauliflower mash.
Watch added sugars and sauces: Avoid sweet glazes or sugary dressings on the side — a squeeze of lemon or a drizzle of olive oil is all this dish needs.
Increase healthy fats if desired: Add a pat of butter on each roll before baking or finish with a drizzle of extra-virgin olive oil after cooking for more fat and flavor.

Equipment & Tools

Baking dish — Something a little wider than the length of the fillets so each roll lays flat and doesn’t crowd.
Mixing bowl — For combining the filling; a large bowl makes it easier to mix evenly.
Measuring spoons and cups — To keep quantities consistent with the recipe.
Paper towels — For patting fillets dry; dryness helps seasoning stick and prevents steam during baking.
Pastry brush or spoon — For brushing olive oil over the rolls.

Steer Clear of These

A few missteps will cost texture or flavor. Avoid them:

Skipping the pat dry step: Don’t skip drying the fillets. Excess moisture discourages browning and can make rolling slippery.
Overfilling the fillets: If you use too much filling the filet may not roll cleanly and could leak during baking. Divide into six equal portions as directed.
Baking too hot or too long: Flounder cooks quickly. Higher temperatures or extended time will dry the fish out. Stick close to 350°F and check for flakiness around 18–22 minutes.

Nutrition-Minded Tweaks

Small substitutions will lower calories, sodium, or saturated fat without losing the core experience:

Reduce cream cheese: Use 2 oz cream cheese and pad the rest of the filling volume with additional spinach or a few tablespoons of Greek yogurt if you want to cut fat and calories.
Lower-sodium feta: Choose a reduced-sodium feta or rinse a standard feta briefly to pull some surface salt if you’re watching sodium.
Lighten the cheese blend: Swap half the mozzarella for part-skim mozzarella to shave a few grams of fat while keeping melt and texture.
Bulk with greens: Add an extra ounce or two of spinach (well-drained) to increase fiber and volume with minimal calories.

Pro Tips & Notes

Prep and assembly

Softening the cream cheese ahead of mixing ensures a smooth, spreadable filling. If your spinach is very wet, press it in a clean towel or spin it in a salad spinner. A wetter filling will make rolling harder and encourage the filling to escape.

Rolling technique

Place the filling toward the tail end of the fillet. Rolling from the tail toward the head keeps the seams tucked under. Place each roll seam-side down in the baking dish so they hold their shape while baking.

Browning and finish

The olive oil brushed on top helps with a gentle sheen and light color. If you want a touch more color, slide the finished dish under the broiler for 30–60 seconds — watch closely so the cheese doesn’t burn.

Timing and doneness

Ovens vary. Start checking at 18 minutes. The fish is done when it flakes easily with a fork and is opaque through the center. A quick rest of 2–3 minutes after baking helps juices redistribute and keeps the filling from running.

How to Store & Reheat

Cool any leftovers to room temperature no longer than two hours after cooking, then cover and refrigerate.

Refrigerator: Store in an airtight container for up to 3 days.
Freezer: I don’t recommend freezing once baked; the texture of the filling and fillets degrades. If you plan to freeze, assemble unbaked rolls, freeze on a tray until firm, then transfer to a freezer bag and bake from frozen (add 8–12 minutes to cook time and check doneness).
Reheat: Reheat in a 325°F oven for 8–12 minutes (covered) until warmed through. Microwaving works for quick reheats but can make the fish softer; microwave on medium power in 30-second intervals, then finish in a hot oven if you want the exterior firmer.

The Takeaway

Spinach Stuffed Flounder is a reliable, fast, and tasty dish that looks elegant with very little fuss. With a simple cheese-and-spinach filling, lightly seasoned fillets, and a short bake, you get a meal that feels special but is comfortable to make any night of the week. Keep the key steps in mind — dry the fish, portion the filling evenly, and watch the oven — and you’ll get consistently delicious results.

Serve it alongside a bright salad, some lemon-scented grains, or roasted vegetables. Little decisions like a lemon wedge or a fresh herb garnish will elevate the plate without complicating the prep. Enjoy the simplicity and the payoff: a warm, flaky fish with a satisfying, creamy center that family and guests will appreciate.

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