Mixed Vegetable Casserole

This delectable mixed vegetable casserole is simple to make with frozen vegetables. 

Instead of canned soup, mayonnaise, or other processed ingredients, it features a rich, creamy, homemade Mornay cheese sauce full of flavor from a touch of white wine, Parmesan, and Gruyere cheese. 

My vegetable casserole is comfort food, perfect for a weeknight dinner or holiday side dish. Even the non-vegetable eaters in the crowd will love it.

Why You’ll Love This Recipe

This recipe has been a family favorite for years. My mom made it for every holiday when I lived at home. I think you’ll love it too because:

• It’s easy to make, and you can prepare it ahead and bake it before dinner.
• This recipe is a tasty way to eat more vegetables. 
• The creamy, decadent sauce is made with whole, unprocessed ingredients.
• As much as I love roasted vegetables, a creamy vegetable casserole always feels like a special treat.

Mornay sauce is a classic French sauce and a variation of Bechamel sauce. You'll love the flavor so much.

But don't let the thought of a French sauce scare you. It's basically a version of the cheddar cheese sauce you make for mac and cheese. And it literally takes 5 minutes to make.

Recipe Ingredients

Here's what I use to make my mixed vegetable casserole. Substitutions and a few variations are listed in the section below. 

Mixed vegetables. I use frozen mixed vegetables with carrots, peas, green beans, and corn. Nearly every grocery store carries them, and they work well here.

Milk for the sauce. I usually have low-fat milk in my fridge, so that's what I use. Whole milk will make it creamier, but the sauce is plenty rich with low-fat milk. You don’t need cream.

Dried garlic powder, thyme, and nutmeg. No need to use fresh garlic or herbs. These pantry staples tie the sauce flavors together nicely.

Grated Parmesan and shredded Gruyere or Swiss cheese. These two cheeses are classic components of a Mornay sauce.

Homemade breadcrumbs. Homemade tastes much better than crushed crackers or packaged breadcrumbs. If you have part of a loaf of bread at the end of its life, tear up what's left and store it in the freezer. Then you'll always have homemade breadcrumbs. I like to keep the bread pieces on the larger side (about ½ inch), but you can make also them smaller and more crumb-like.

Substitutions and Variations

For the vegetables: You can use any frozen vegetable mixture or stick to one or two vegetables. You can also use fresh vegetables. If using fresh, chop them all to a similar small size. You'll also have to cook hard vegetables like fresh carrots or cauliflower for longer until they're fork-tender. 

Great vegetable options include:

• Rainbow or regular orange carrots
• Parsnips
• Sweet potatoes
• Butternut squash
• Broccoli
• Cauliflower
• Zucchini
• Green beans
• Red peppers

Another alternative is to use a variety of fresh and/or frozen vegetables. I've used chunks of precooked sweet potatoes and mixed them with frozen peas, corn, green beans, and Romanesco cauliflower from Trader Joe's. Feel free to be creative.

For the cheese: If you don’t want a classic mornay sauce, substitute a good quality, sharp cheddar for the Gruyere cheese and make a cheddar cheese sauce instead. 

Step By Step Instructions

First, steam your vegetables just until they’re fork-tender but still crisp (about three minutes). They’ll finish cooking in the oven. Do not overcook them; they’ll turn mushy and lose their bright color. Season them while they cook. Drain them and place them in a casserole dish.

Second, prepare your Mornay sauce. Melt the butter and sprinkle the flour over it. Whisk well to combine and let it bubble for a minute, but don’t let it turn brown. Gradually whisk in the milk and spices.

Let the sauce come to a simmer while whisking. It will get thick and creamy once it starts to bubble. Add the cheese in a little bit at a time and keep whisking it until the cheese melts and everything is smooth.

Third, pour the sauce over the vegetables. No need to stir it. Pick up the casserole dish and give it one or two taps on the counter to let the sauce sink through the vegetables. It will look like there's a LOT of sauce, but it thickens up as it bakes.

Sprinkle the bread crumbs over the top and put it into the oven to bake.

Fourth, bake the mixed vegetable casserole until the sauce is bubbly and the bread crumbs are golden brown.

Expert Tips

Larger pieces of fresh vegetables need more time to steam. Keep an eye on them and steam them until they're just tender enough to insert a fork or knife tip partly into most pieces. The vegetables will finish cooking in the oven.

Take care not to let the butter or flour brown when making the mornay sauce. Whisk the flour and butter well to smooth out any lumps before adding the milk. And add the milk slowly while whisking so your cause doesn’t clump.

Lightly cover the casserole with foil for the first few minutes in the oven so the breadcrumbs don't brown too fast. I remove it for the last 15 minutes. If the breadcrumbs aren't golden enough, place the casserole under a hot broiler for 30 seconds or so.

The sauce will tighten and thicken as the vegetable casserole cools, so don't worry if it seems too saucy when you take it out of the oven.

What Goes With Mixed Vegetable Casserole?

I LOVE this recipe with beef tenderloin for a special holiday treat. Something about the cheesy, wine-flavored sauce and the beef just works. 

But you can also serve it with a roasted chicken or turkey. If you’re looking for easy, homemade Thanksgiving or holiday recipes, this one is a perfect side dish.

This vegetable casserole also works as a stand-alone vegetarian meal. It's got all of the food groups!

Recipe FAQs

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Recipe

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Eat well!