Broccoli Spinach Casserole (with a French Onion Twist)

A broccoli spinach casserole is a creamy, cheese-baked side dish made from steamed broccoli, well-drained spinach, sour cream, condensed soup, and melted cheddar, baked until bubbly and golden. It works as a vegetable side for almost any dinner, and swapping the topping for crispy fried onions turns it into a broccoli casserole with French onions.

Explore more practical ideas in our vegetarian dinners.

What Makes a Broccoli Spinach Casserole Work

The texture of this dish depends on moisture control more than any other single factor. Frozen spinach holds a surprising amount of water, and if you skip squeezing it dry, the casserole turns watery instead of creamy. Fresh or frozen broccoli should be just tender-crisp before it goes into the dish, since it will continue cooking in the oven and can turn mushy if it's already soft going in.

The creamy base — sour cream, a condensed soup, eggs, and shredded cheese — binds the vegetables together and sets as it bakes. Eggs are what give the casserole its sliceable, custardy structure rather than a loose, soupy texture.

Broccoli Casserole with French Onions: The Topping Variation

Swapping a plain breadcrumb or cracker topping for crispy fried onions is what turns a standard broccoli spinach casserole into a broccoli casserole with French onions. The onions are added in the last 10 to 15 minutes of baking, not at the start, so they crisp up instead of steaming soft under the lid. If you want extra crunch, reserve half the onions and sprinkle them on right after the casserole comes out of the oven.

Other Topping Options

• Panko breadcrumbs tossed with a little melted butter for a lighter crunch
• Crushed cheese crackers for extra richness
• Extra shredded cheddar alone, for a simpler cheese-crusted top

Ingredient Substitutions for Broccoli Spinach Casserole

Fresh spinach can replace frozen: use about 10 ounces of fresh leaves, wilt them in a hot pan first, then drain and press out the liquid the same way you would with thawed frozen spinach. Cream of mushroom soup can be swapped for cream of chicken soup if you're not keeping the dish vegetarian. Cottage cheese can stand in for part of the sour cream for a slightly lighter, tangier filling. Any melting cheese — Monterey Jack, a Swiss-cheddar blend, or mozzarella — can replace some or all of the cheddar.

Preventing a Watery or Underset Broccoli Spinach Casserole

Most failures come down to moisture or undercooking. Squeeze thawed spinach by hand or in a clean kitchen towel until no more liquid releases. Drain steamed broccoli thoroughly and let it steam off excess moisture for a minute before mixing it in. Bake until the center is set rather than jiggly, and use an instant-read thermometer to confirm the center of the casserole reaches at least 160°F (71°C) before pulling it from the oven, since the dish contains eggs.

Storing and Reheating Broccoli Spinach Casserole

Cooled casserole keeps well covered in the refrigerator for up to 4 days. For longer storage, freeze portions in an airtight container for up to 2 months; thaw overnight in the refrigerator before reheating. When reheating leftovers, warm them in the oven or microwave until the center reaches 165°F (74°C).

Serving a Broccoli Spinach Casserole

This casserole works as a side dish alongside roasted or grilled proteins, or as a main course on its own with a simple salad. If you're planning a full vegetarian dinner around it, the guide to choosing tonight's vegetarian dinner has more ideas for pairing side dishes like this one with a complete meal.

Safe internal temperatures in this recipe follow the FoodSafety.gov safe minimum internal temperature chart.