If you love a good mushroom Swiss burger, this one’s for you, just without the bun. Browned ground beef, soft mushrooms, and onion get stirred into a creamy sour cream and Swiss cheese mixture, then baked in a 9×13 dish until the top is bubbly and golden.

It is low carb, it uses one skillet and one baking dish, and it is on the table in under an hour. The ingredient list is short and easy to find at any grocery store. No weird ingredients, no complicated steps. Just a hearty, cheesy dinner that works for keto eaters and everyone else at the table.

Why This Keto Mushroom Swiss Beef Bake Works

A mushroom Swiss burger gets its flavor from three things: well-browned beef, deeply cooked mushrooms, and melty Swiss cheese. This bake keeps all three and drops the bun. Cooking the beef, mushrooms, and onion together in one skillet lets the mushrooms soak up the beef fat and seasoning, so every bite tastes like the burger.

Sour cream takes the place of a flour-based sauce. It makes the filling creamy and a little tangy without adding carbs. Half the Swiss melts into the filling to bind it together, and the other half goes on top, where it browns in the oven. Swiss is a mild, nutty cheese that melts smoothly, so it does not turn greasy the way some sharp cheeses can.

Ingredients and Easy Swaps

Ground beef: The recipe uses about 1 1/2 pounds. An 80/20 or 85/15 blend gives the best burger flavor. If you use 80/20, drain off most of the fat after browning, but leave a tablespoon or two in the pan for flavor. Ground turkey works too, though it is milder.

Sliced mushrooms: White button or baby bella (cremini) mushrooms both work. Baby bellas have a deeper, meatier taste. Buying them pre-sliced saves about 5 minutes of prep.

Onion and garlic powder: One small onion adds sweetness without many carbs. Yellow or white onion both work. You can swap the garlic powder for 2 cloves of fresh minced garlic. Add it in the last minute of browning so it doesn’t burn.

Sour cream: Full-fat sour cream is best for keto and for texture. Light sour cream can turn watery in the oven. Cream cheese, softened and stirred in, is a good swap and makes the filling even richer.

Swiss cheese: Two cups shredded. Shredding your own from a block melts more smoothly than bagged cheese, which has anti-caking starch on it. Gruyère is a great swap if you want a stronger, nuttier flavor. Provolone also works.

How to Make It at a Glance

1. Heat the oven to 375°F and grease a 9×13-inch baking dish.
2. Brown the beef with the mushrooms, onion, garlic powder, salt, and pepper until the beef is no longer pink and the vegetables are soft.
3. Take the skillet off the heat and stir in the sour cream and half the Swiss cheese.
4. Spread the mixture in the dish and top with the rest of the cheese.
5. Bake 25 to 30 minutes, until bubbly and lightly golden. Top with chives if you like.

Common Mistakes to Avoid

Not cooking the mushrooms long enough. Mushrooms give off a lot of water. Keep cooking until that liquid is gone and the mushrooms start to brown. If you stop early, the water ends up in your baking dish and the bake turns soupy.

Skipping the drain. Too much beef fat will pool on top of the cheese. Tilt the pan and spoon off extra fat before you add the sour cream.

Adding sour cream over high heat. Sour cream can split if it boils. Pull the skillet off the burner for a minute before stirring it in.

Undercooking the beef. Ground beef should reach 160°F. Make sure there is no pink left in the skillet before it goes into the oven.

Variations

Bacon mushroom Swiss: Cook 4 to 6 slices of bacon first, crumble it, and stir it into the filling. Use a little of the bacon fat to cook the mushrooms.

Add a vegetable: Stir in 2 cups of chopped fresh spinach at the end of browning, or add a cup of small cauliflower florets. Both keep it low carb.

Steakhouse style: Add 1 tablespoon Worcestershire sauce and 1/2 teaspoon dried thyme to the beef while it browns.

Not keto: If you are not counting carbs, stir in 2 cups of cooked egg noodles before baking for a heartier casserole.

What to Serve With It

To keep the meal low carb, serve it with a crisp green salad, roasted green beans, or steamed broccoli with butter. Cauliflower mash is a nice match too, since it soaks up the creamy filling. If carbs are not a concern, mashed potatoes or a slice of crusty bread works well.

Make Ahead, Storage, and Reheating

You can assemble the bake up to 1 day ahead. Cover the dish and keep it in the fridge. When you are ready, bake it straight from the fridge and add 5 to 10 minutes to the bake time.

Leftovers keep in an airtight container in the fridge for 3 to 4 days. You can freeze cooled portions for up to 2 months. The sour cream may be a little grainy after freezing, but the flavor holds up. Thaw overnight in the fridge.

Reheat single portions in the microwave for 1 to 2 minutes, stirring halfway. For a larger amount, cover with foil and warm in a 350°F oven for 15 to 20 minutes, until hot in the center.

Frequently Asked Questions

How many carbs are in this beef bake?
Most of the carbs come from the onion, mushrooms, and sour cream. Split into 4 servings, it lands at a low number per serving. Check the labels on your sour cream and cheese, since brands vary.

Can I use a smaller pan?
Yes. An 8×8 or 9×9 pan makes a thicker bake. Add about 5 minutes to the bake time and look for bubbling around the edges.

Why is my bake watery?
Usually the mushrooms were not cooked down enough, or the beef fat was not drained. Let it rest for 5 minutes after baking and it will thicken a bit as it cools.

Can I use canned mushrooms?
You can. Drain them well and pat them dry. Fresh mushrooms give a better texture and more flavor, but canned works in a pinch.