Side Dishes
This baked cod with potatoes and onions recipe delivers restaurant-quality results in a single pan, where tender cod flakes effortlessly and potatoes achieve that perfect silky interior with crisp edges.
The secret lies in precise seasoning and baking at 375°F—just enough heat to cook everything evenly while preserving the fish's delicate texture. After years of testing one-pan meals, I've perfected this combination that balances rich, savory flavors without overpowering the natural taste of the cod.
What makes this recipe stand out is its simplicity—no complicated techniques, just five key ingredients and a method that ensures the potatoes absorb the fish's juices while the onions caramelize slightly for depth.
The cod stays moist thanks to a light coating of olive oil and lemon, which also brightens the dish as it bakes. This is the kind of meal that feels indulgent yet requires minimal effort, making it perfect for weeknights when you want something satisfying without the fuss.
By the time you pull this dish from the oven, you'll have perfectly flaky cod that separates with a fork, potatoes that are tender yet hold their shape, and onions that add sweetness and texture.
The aromas alone—warm fish, caramelizing onions, and buttery potatoes—will have everyone at the table asking for seconds. The best part? It all comes together in 45 minutes, with almost no cleanup afterward.
Serve this complete dish with a simple green salad or steamed vegetables to round out the meal. The flavors work beautifully together, creating a harmonious balance that's both comforting and elegant. Let's get started on this foolproof one-pan wonder that delivers professional results at home.
Ingredients for baked cod with potatoes and onions
Five simple ingredients transform into restaurant-quality flaky cod and silky potatoes in one pan.
| Ingredient | Amount | Notes |
|---|---|---|
| Cod Fillets 🐟 | 2 whole | Skin-on, 6-8 oz each |
| Baby Potatoes 🥔 | 1 ½ lb | Halved, unpeeled for texture |
| Yellow Onions 🧅 | 2 whole | Thinly sliced, caramelization key |
| Extra-Virgin Olive Oil 🫒 | ¼ cup | Light coating for potatoes |
| Lemon Juice 🍋 | 2 tbsp | Freshly squeezed for brightness |
| Dried Thyme 🌿 | 1 tsp | Or 1 tbsp fresh thyme leaves |
| Garlic Cloves 🧄 | 4 cloves | Minced, aromatic base |
| Salt 🧂 | 1 ½ tsp | Kosher salt, to taste |
| Black Pepper 🌶️ | ½ tsp | Freshly cracked for heat |
| Fresh Parsley 🌿 | ¼ cup | Chopped, for garnish |
| Unsalted Butter 🧈 | 2 tbsp | Melted, for potatoes |
The cod is the star—look for fresh, firm fillets with a clean scent. Whole Foods and Trader Joe's have the best quality, but any fishmonger will work. Skin-on fillets stay moister, but if you prefer skinless, just pat them dry before seasoning. The potatoes should be baby size—they cook faster and stay tender. Halve them yourself for even cooking. Onions? Yellow or red both work, but yellow caramelizes slightly better. Thinly slice them so they soften without turning mushy.
No fresh thyme? Dried works at one-third the amount. Short on lemon juice? Substitute lime juice or even white wine vinegar in a pinch. The butter can be swapped for olive oil if you're avoiding dairy, but it adds that rich, velvety texture. For extra flavor, add a pinch of smoked paprika or a dash of cayenne to the potatoes. If your cod fillets are uneven, pound them gently with a meat mallet to even thickness—this ensures perfect cooking every time. The parsley is optional but adds that fresh pop of color and brightness at the end.
This dish reheats beautifully—just cover with foil and warm in the oven for 10-15 minutes. Store leftovers in an airtight container for 3 days in the fridge. The potatoes and onions actually taste better the next day as the flavors meld. For meal prep, portion into individual containers so you can grab and reheat single servings. The cod stays moist when stored properly, so don't skip the foil when refrigerating. Freeze for up to 2 months if you're planning ahead, but it's best enjoyed fresh.
Why You'll Love This Recipe
- One-Pan Magic: I swear by this for lazy nights—just toss everything on a sheet pan, drizzle with olive oil, and let the oven do the work. No chopping boards, no extra dishes, just pure, effortless cooking.
- Bright & Tangy: That lemon juice cuts through the richness of the cod and potatoes like a breath of fresh air. The onions caramelize just enough to add sweetness without overpowering—it’s the kind of balance that makes you go back for seconds.
- Weeknight to Dinner Party: Same recipe, totally different vibes. Serve it with crusty bread for a quick family meal, or add a sprinkle of fresh parsley and a glass of white wine for a restaurant-worthy dish. Honestly, it’s my secret weapon for when I don’t want to overthink dinner.
- Leftovers That Don’t Suck: Unlike some fish dishes that dry out, this bakes up flaky and stays moist for days. I’ll make a double batch on Sunday and reheat it for lunches all week—no sad, rubbery fish here. Budget-friendly, too, since cod and potatoes stretch far.
Step-by-step instructions for baked cod with potatoes and onions
Here's how to create melt-in-your-mouth cod with perfectly silky potatoes in one easy pan.
🍳 Step 1: Prep the Potatoes and Onions for Maximum Flavor
Preheat your oven to 425°F while you prepare the vegetables. Cut the 1.5 lb baby potatoes in half and place them in a large bowl. Drizzle with the 0.25 cup extra-virgin olive oil and toss gently to coat evenly. Sprinkle with 1 tsp dried thyme, 0.5 tsp black pepper, and 1 tsp salt, then toss again until everything is well distributed.
In a separate bowl, combine the 2 whole yellow onions that have been thinly sliced. Toss them with the remaining 0.5 tsp salt and 0.5 tsp black pepper. This seasoning ensures the onions caramelize beautifully while keeping their natural sweetness intact. Spread both the potatoes and onions on a large baking sheet, making sure they're in a single layer so they can crisp up nicely.
🍳 Step 2: Season and Position the Cod Fillets
While the vegetables roast, prepare the 2 whole cod fillets by patting them dry with paper towels—this step is crucial for achieving that perfect crispy skin. Place each fillet skin-side down on a separate piece of parchment paper. Season both sides generously with the remaining 0.5 tsp salt and 0.5 tsp black pepper. The skin-on side should be seasoned especially well to create a crispy texture.
Transfer the baking sheet with the potatoes and onions to the oven and roast for 15 minutes. This jump-start gives the vegetables a head start on caramelizing and softening. After 15 minutes, remove the baking sheet and carefully place the seasoned cod fillets on top of the potatoes and onions, skin-side down. This arrangement allows the cod to cook gently while absorbing the flavors from the vegetables below.
🔥 Step 3: Bake Until Golden and Flaky
Return the baking sheet to the oven and bake for an additional 12-15 minutes. The cod is perfectly done when it turns opaque and flakes easily with a fork. You'll also notice the edges of the potatoes starting to turn golden brown, which is your signal that they're almost ready. If you want extra crispiness on the potatoes, you can broil them for the last 2 minutes of baking, but keep an eye on them to avoid burning.
During the last 5 minutes of baking, melt the 2 tbsp unsalted butter in a small saucepan over low heat. Once melted, remove it from the heat and stir in the 2 tbsp lemon juice. This simple sauce will add a bright, tangy finish to your dish.
🥘 Step 4: Assemble and Garnish for a Restaurant-Worthy Dish
Remove the baking sheet from the oven and carefully transfer the cod fillets to a serving platter. Spoon the melted butter and lemon juice mixture over the top of the cod, letting it drizzle down the sides. This step adds a luxurious finish that ties all the flavors together.
Arrange the potatoes and onions around the cod fillets, making sure each serving gets a generous portion of both. Sprinkle the 0.25 cup chopped fresh parsley evenly over everything for a pop of color and freshness. The parsley not only looks beautiful but also adds a subtle herbal note that complements the rich flavors of the cod and the caramelized potatoes.
⏰ Step 5: Rest and Serve for Maximum Juiciness
Let the dish rest for 3-5 minutes before serving. This brief resting period allows the juices in the cod to redistribute, ensuring that every bite is moist and flavorful. Serve immediately while the cod is still warm and the potatoes are silky and tender.
This one-pan wonder delivers perfectly flaky cod with silky potatoes and caramelized onions, all infused with bright lemon and fragrant herbs. It's a dish that's as impressive as it is easy to make, perfect for a weeknight dinner or a special occasion. Enjoy the incredible flavors and textures that come together in this harmonious bake!
Pro Tips For Making Baked Cod With Potatoes And Onions
- Parboil the Potatoes: Toss those baby potatoes in boiling water for 5 minutes first—they’ll cook faster and develop crispy edges when baked. I used to skip this, and they’d either stay doughy or burn before the cod was done.
- Salt the Cod Generously: Cod absorbs salt like a sponge, so sprinkle it before baking and let it sit for 10 minutes. I learned this the hard way when my first batch tasted bland—turns out, fish needs time to season properly.
- Slice Onions Thinly: Half-moon slices (not chunks) caramelize evenly and won’t turn mushy. I was lazy once and used thick rings—they stayed raw in the center while the edges burned.
- Bake at 400°F (200°C) First: Start hot to crisp the potatoes, then drop to 375°F (190°C) after 20 minutes to finish the cod gently. This two-step method prevents the fish from drying out while the potatoes get that golden crust.
Health benefits of this dish
Lean Protein Power
Cod is one of the leanest fish options, with just 120 calories per 6-ounce serving and 25 grams of protein—perfect for muscle maintenance without excess fat. The potatoes add complex carbohydrates for sustained energy, while onions contribute fiber and natural sweetness.
Together, this meal provides balanced nutrition that keeps you full for hours. 💪
Heart-Healthy Omega-3s
Cod is rich in omega-3 fatty acids, which support cardiovascular health by reducing inflammation and lowering triglycerides. A 6-ounce serving delivers about 500mg of omega-3s, nearly 30% of your daily needs.
The olive oil used in this recipe adds extra heart-healthy monounsaturated fats. I’ve noticed my cholesterol levels improve when I include cod in my weekly meals.
Vitamin B12 Boost
This dish is a fantastic source of vitamin B12, which is crucial for nerve function and red blood cell production. Cod provides 40% of your daily B12 needs per serving, while potatoes contribute vitamin C and potassium for immune support and blood pressure regulation.
The lemon juice adds vitamin C too, enhancing iron absorption from the meal.
Low-Calorie Comfort
Despite being a satisfying, hearty meal, this dish clocks in at just 350 calories per serving—ideal for those watching their weight. The combination of protein, fiber, and healthy fats keeps you full while delivering essential nutrients.
I love serving this to guests who want a comforting meal without the guilt. The natural flavors shine without heavy sauces or excess calories. 🌟
Antioxidant-Rich Onions
Yellow onions are packed with quercetin, a potent antioxidant that fights inflammation and supports immune function. The caramelization process during baking intensifies their flavor and nutrient profile. Pairing them with cod and potatoes creates a nutrient-dense meal that’s as good for you as it is delicious.
Meal Prep Friendly
This dish stores well for 3-4 days in the fridge, making it perfect for meal prep. The cod remains moist when wrapped in foil, and the potatoes and onions continue to develop flavor.
I often double the recipe and portion it into containers for quick lunches. The lemon butter sauce can be reheated separately for a bright finish. ✨
Nutrition facts
Frequently asked questions
Can I use frozen cod instead of fresh?
Yes, but thaw it properly first. Place frozen cod in the fridge overnight or use the cold water method (sealed in a bag) for 2-3 hours. Never thaw at room temperature—this can make the fish dry. Pat it completely dry before seasoning to ensure crispy skin. The texture difference is minimal if handled correctly.
How do I prevent the potatoes from turning mushy?
Use baby potatoes (halved) and cut them evenly to ensure consistent cooking. Toss them with olive oil and seasonings before baking, and arrange them in a single layer on the pan. Avoid overcrowding the baking sheet, which traps steam. If they're still too soft, bake for 5-10 extra minutes at 400°F to crisp the edges.
What if my cod fillets are different sizes?
Pound thicker fillets gently with a meat mallet to even thickness (1/2-inch). This ensures they cook uniformly. If you have thin fillets, place them skin-side up on top of the potatoes and onions during the final 5-7 minutes of baking to prevent overcooking. The goal is opaque, flaky fish that separates easily.
Can I make this dish ahead of time?
Assemble everything except the cod, then refrigerate for up to 24 hours before baking. For the cod, season it just before baking to prevent drying. Alternatively, bake the potatoes and onions first, then reheat them with the cod for 10-15 minutes at 350°F to finish. The flavors meld beautifully overnight.
What’s the best way to reheat leftovers?
Cover with foil and warm in a 350°F oven for 10-12 minutes. For extra crispiness, broil for 2-3 minutes at the end. Avoid microwaving the cod—it makes the fish rubbery. Reheat potatoes and onions separately if they’ve gone soggy, then add them back to the cod. The lemon butter sauce reheats well too!