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Creamy Vegetable Casserole

A warm, hearty baked vegetable casserole packed with tender vegetables wrapped in a rich, velvety cream sauce topped with golden breadcrumbs and Parmesan. A fuss-free weeknight dinner that tastes like you spent hours on it.
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Prep Time 15 minutes
Cook Time 35 minutes
Servings: 6
Calories: 280
Ingredients Method Notes

Ingredients
  

Casserole
  • 2 tablespoons unsalted butter
  • 1 medium yellow onion, diced
  • 3 cloves garlic, minced
  • 2 cups broccoli florets
  • 1 cup cauliflower florets
  • 1 cup sliced zucchini
  • 1 cup frozen peas
  • 1 cup diced carrots
  • 3 tablespoons all-purpose flour
  • 2 cups whole milk (or unsweetened oat milk)
  • 1 cup low-sodium vegetable broth
  • 1 cup shredded sharp cheddar cheese
  • ½ cup sour cream
  • 1 teaspoon garlic powder
  • ½ teaspoon onion powder
  • salt and black pepper to taste
Topping
  • ½ cup breadcrumbs
  • 2 tablespoons grated Parmesan cheese

Method
 

Preheat and Prep
  1. Preheat your oven to 375°F (190°C) and lightly grease a 9x13-inch baking dish with butter or cooking spray.
Sauté the Aromatics
  1. Melt the butter in a large oven-safe skillet or heavy-bottomed pot over medium heat. Add the diced onion and cook for about 3–4 minutes until it softens and turns translucent.
  2. Add the minced garlic and stir for another minute until fragrant.
Build the Cream Sauce
  1. Sprinkle the flour over the butter and onion mixture, stirring constantly for about 1–2 minutes to cook out the raw flour taste.
  2. Slowly pour in the vegetable broth while whisking, then gradually add the milk. Keep whisking over medium heat until the sauce thickens noticeably — about 4–5 minutes. It should coat the back of a spoon.
  3. Remove from heat and stir in the shredded cheddar and sour cream until the sauce is silky smooth. Season generously with salt, pepper, garlic powder, and onion powder.
Add the Vegetables
  1. Fold in all the vegetables — broccoli, cauliflower, zucchini, carrots, and peas — until every piece is coated in the creamy sauce.
  2. Pour the entire mixture into the prepared baking dish and spread it out into an even layer.
Top and Bake
  1. Combine the breadcrumbs and Parmesan cheese in a small bowl, then sprinkle the mixture evenly over the top of the casserole.
  2. Bake uncovered for 25–30 minutes, until the top is golden brown and bubbling at the edges.
  3. Let the casserole rest for 5 minutes before serving to allow the sauce to settle.

Notes

Substitution Tips: Swap sour cream for cream cheese for an even richer sauce. Use gluten-free flour and breadcrumbs to make this casserole gluten-free. For picky eaters, replace zucchini with corn. Meal-Prep Tip: Chop all vegetables the night before and store in an airtight container in the fridge. Common Mistakes: Don't skip the roux step; thaw and pat dry frozen vegetables before use; don't overbake; season the sauce generously before adding vegetables. Storage: Store leftovers in an airtight container in the refrigerator for up to 4 days. Freeze portioned cooled casserole in freezer-safe containers for up to 2 months. Reheat at 350°F covered with foil. Make-Ahead: Assemble, cover tightly, and refrigerate up to 24 hours before baking; add 5–10 extra minutes to bake time.