Clam Chowder and Veggie Casserole: The Easiest One-Pan Dinner You’ll Make This Week

There is a type of recipe that doesn’t ask much of you but gives you everything back. That’s what Clam Chowder and Veggie Casserole is. You don’t need any cooking skills, special tools (other than a deep dish baking pan), or complicated techniques to make this dish. But when it comes out of the oven, it’s warm, filling, and deeply satisfying, as if you spent hours carefully preparing it. This is the best way to cook on a weeknight.

The recipe is based on a great idea: instead of using a can of Progresso Chunky New England Clam Chowder as soup, use it as a sauce. When you pour it over a bed of seasoned onions and roasted frozen vegetables and then bake it, it turns into a creamy, savory binder that holds the whole casserole together. By seasoning the onions, then the vegetables, and finally covering everything with a thick layer of Parmesan, you make sure that every bite is full of flavor, not just the outside.

The fact that you don’t have to do anything while the food cooks is what makes this recipe so great for busy families. You don’t have to do much once the pan is in the oven. You take the pan out for two short check-ins, stir or add ingredients, and then put it back in. That’s all. No stirring at the stove, no babysitting a sauce, and no watching water boil. You can do anything else while the oven does its job.

It can also be used in many ways. You can use any vegetables you have on hand instead of the frozen mixed vegetable bag. You can switch out the Parmesan topping for sharp cheddar, mozzarella, or a spicy mix, depending on how you feel. You can change the amount of seasoned salt. It’s surprising how much you can change a recipe with so few ingredients. This casserole is easy to make and tastes great, whether you’re feeding your family on a Tuesday night or bringing something comforting to a potluck.

Recipe at a Glance

Detail	Info
Cuisine	American
Course	Main Course
Difficulty	Easy
Servings	4
Prep Time	10 minutes
Cook Time	75 minutes
Calories per Serving	Approx. 290 kcal

Ingredients

• 1 deep dish baking pan
• 1 can Progresso Chunky New England Clam Chowder
• 1 white onion
• 1 bag frozen mixed vegetables
• Avocado oil (or another high-heat neutral oil), enough to coat the bottom of the pan
• Parmesan cheese, for topping (or another cheese of your choice)
• Lawry’s Seasoned Salt, to taste
• Aluminum foil, for lining the pan

Instructions

Step 1: Preheat and Prepare the Pan

Set your oven to 400°F (200°C) and allow it to fully preheat before anything goes in. While the oven heats, line your deep dish baking pan with aluminum foil. The foil serves two purposes here: it makes cleanup dramatically easier, and it helps conduct heat more evenly through the base of the casserole. Once the pan is lined, drizzle avocado oil generously over the foil and spread it around to coat the entire bottom surface. This prevents sticking and gives the vegetables a light, slightly crisped base as they roast.

Step 2: Prepare and Season the Onion

Peel the white onion and cut it into half-rings — not too thin, not too thick. You want pieces that will hold some structure through the long baking time rather than completely dissolving into the casserole. Spread the onion rings evenly across the bottom of the oiled pan, making sure they form a fairly even layer. Season them directly with Lawry’s Seasoned Salt. This step is intentional and important: seasoning in layers builds flavor at every level of the dish rather than relying on a single seasoning pass at the end.

Step 3: Add and Season the Frozen Vegetables

Pour the entire bag of frozen mixed vegetables over the seasoned onion layer. There’s no need to thaw the vegetables beforehand — they’ll release their moisture as they roast in the oven, which actually helps build the savory liquid base that the chowder will later blend into. Spread them out into an even layer across the pan and season again with Lawry’s Seasoned Salt. Don’t skip this second round of seasoning — it’s what prevents the finished dish from tasting flat.

Step 4: First Bake — 30 Minutes

Place the pan in the preheated 400°F oven and bake uncovered for 30 minutes. During this time, the onions will soften and begin to caramelize at the edges, and the frozen vegetables will thaw, roast, and develop a little color. The oven is building the base flavor of the casserole during this stage, so resist the urge to open the door and check on things too early.

Step 5: Add the Clam Chowder

After 30 minutes, carefully pull the pan out of the oven. Open the can of Progresso Chunky New England Clam Chowder and pour it directly over the vegetables. Use a spoon or spatula to gently mix the chowder into the vegetable and onion layer so it coats everything evenly. The chowder at this stage is quite thick — and that’s fine. It will loosen slightly as it continues to bake and absorb the moisture released by the vegetables. Return the pan to the oven.

Step 6: Second Bake — 30 Minutes

Bake for another 30 minutes. During this stage, the chowder melds into the vegetables, the flavors deepen and concentrate, and the casserole begins to look and smell like something truly special. The clam and cream base will thicken into a saucy, coating consistency that clings to the vegetables and onions.

Step 7: Add the Cheese Topping

Pull the pan out of the oven once more. This is the final build. Coat the entire top surface of the casserole generously with Parmesan cheese. Be liberal here — a thin dusting won’t give you the golden, savory crust you’re looking for. If you’re using a different cheese like cheddar or mozzarella, shred it and layer it on thickly. Return the pan to the oven.

Step 8: Final Bake — 15 Minutes

Bake for a final 15 minutes until the cheese on top is melted, golden, and bubbling at the edges. Remove from the oven and allow the casserole to rest and cool for at least 5 to 10 minutes before serving. This resting time is important — it allows the sauce to settle and thicken slightly so the casserole holds together better when scooped. Add extra Parmesan over individual servings at the table if desired.

Tips for the Best Results

• Don’t skip layered seasoning. Seasoning the onions and the vegetables separately before baking is what makes this dish taste fully developed rather than one-dimensional. Underseasoning at this stage cannot be fixed at the end.
• Use a deep dish pan. A shallow baking sheet won’t contain the chowder properly once it’s poured in. A deep dish pan keeps everything contained and allows the sauce to pool and coat the vegetables evenly.
• Rest before serving. The casserole will look loose right out of the oven. Giving it 5–10 minutes to rest allows the sauce to settle and thicken into a proper scoopable consistency.
• Customize the vegetable mix. A standard frozen mixed vegetable bag typically contains peas, carrots, corn, and green beans — all of which work beautifully here. You can also swap in frozen broccoli florets, cauliflower, or diced frozen butternut squash for variation.

FAQs

Can I use a different brand of canned clam chowder? Yes. Progresso Chunky New England Clam Chowder is specified here because its chunky texture and thicker consistency work well as a casserole sauce. However, other brands of New England-style clam chowder will work as long as they have a creamy, full-bodied consistency. Avoid broth-style or very watery chowders, as they won’t provide enough body to coat the vegetables properly after baking.

Can I add protein to this casserole to make it more filling? Absolutely. Cooked shredded chicken, crumbled cooked sausage, or even bacon bits stirred into the casserole before the second bake would all be excellent additions. Since the clam chowder already provides a small amount of clam meat, additional protein would turn this into a very substantial main course. Keep seasoning in mind — if your added protein is already seasoned, reduce the amount of Lawry’s you use on the vegetables.

How do I store and reheat leftovers? Store leftover casserole in an airtight container in the refrigerator for up to 3 days. To reheat, place individual portions in an oven-safe dish covered loosely with foil at 350°F for about 15 minutes, or microwave in 90-second intervals until heated through. The casserole may thicken further as it sits — add a small splash of milk or broth when reheating to loosen the consistency if needed.

Can this be made dairy-free? The primary source of dairy in this recipe is the canned clam chowder and the cheese topping. Some brands offer dairy-free or reduced-dairy versions of clam chowder, and nutritional yeast or a dairy-free Parmesan alternative can be used as a topping. With those swaps, this recipe can work well for dairy-free diets without significantly changing the preparation method.

What can I serve alongside this casserole? This casserole is hearty enough to serve as a standalone main dish, but it pairs really well with crusty bread or oyster crackers on the side to scoop up the chowder sauce. A simple green salad with a light vinaigrette provides a fresh, acidic contrast to the rich, creamy base. For a more filling spread, serve alongside roasted garlic bread or buttered dinner rolls.

Conclusion

Clam Chowder and Veggie Casserole is the kind of recipe that makes you wonder why you ever spent hours in the kitchen when dinner could be this simple and this good. Five core ingredients, a handful of seasonings, three rounds in the oven, and you have a dish that’s creamy, savory, deeply comforting, and absolutely worthy of a spot in your regular weeknight rotation. It’s the sort of recipe that you share with people who tell you they hate cooking — because if anything is going to change their mind, it’s a casserole that practically makes itself. Serve it hot, pile on the extra Parmesan, and enjoy every bite.