There’s something magical about a skillet full of deeply caramelized onions, earthy mushrooms, and tender sautéed spinach. This Sautéed Spinach, Mushrooms & Caramelized Onions recipe is a powerhouse side dish packed with flavor, nutrients, and versatility — and it comes together using simple ingredients you likely already have in your kitchen.

This combination hits all the right notes: sweetness from slow-cooked onions, savory richness from browned mushrooms, and fresh, vibrant earthiness from spinach. It’s the perfect supporting dish for chicken, steak, pasta, fish, grains, and more — or it can even be served as a vegetarian main when paired with rice, quinoa, or roasted potatoes.

Despite being incredibly easy, this sautéed vegetable medley tastes like something from a cozy bistro. Each vegetable is cooked in its ideal way: the onions are slowly caramelized until silky and golden, the mushrooms are browned until nutty and meaty, and the spinach is added last so it stays bright and tender.

If you’re looking for a go-to vegetable side that is flavorful, nourishing, and beautiful to serve, this dish belongs in your regular rotation.

Why This Dish Works So Well

Caramelized Onions Add Sweet Depth

Low and slow cooking transforms onions into pure flavor gold.

Mushrooms Bring Rich Umami

Browned properly, mushrooms become savory, satisfying, and aromatic.

Spinach Adds Freshness

It balances the richness and adds color and nutrients.

Flexible for Any Meal

Works with breakfast, lunch, dinner — or as a topping for bowls, pasta, or toast.

One Skillet, Fast, and Healthy

Minimal cleanup and ready in under 20–25 minutes.

Ingredients

Vegetables

• 2 large onions, thinly sliced
• 8 oz mushrooms, sliced
• 4–5 cups fresh spinach

Cooking Fats

• 2 tbsp olive oil
• 1 tbsp butter

Seasoning

• 3 cloves garlic, minced
• ½ tsp salt
• ½ tsp black pepper
• ½ tsp dried thyme (or Italian seasoning)
• Red pepper flakes (optional)

Finishing Touches

• Squeeze of lemon
• Fresh parsley (optional)

Instructions

1. Caramelize the Onions
   Heat olive oil and butter in a skillet over medium heat. Add sliced onions and cook 10–12 minutes, stirring often, until deep golden and soft.
2. Add the Mushrooms
   Add sliced mushrooms directly to the skillet. Cook 5–7 minutes until browned and they release then reabsorb their moisture.
3. Add Garlic & Seasoning
   Stir in garlic, salt, pepper, and thyme. Cook 1 minute to bring out the aromatics.
4. Add the Spinach
   Add spinach in batches, stirring as it wilts. Cook until tender but still bright.
5. Finish the Dish
   Add a squeeze of lemon and taste for seasoning adjustments.
6. Serve
   Plate warm with optional parsley.

Sautéed Spinach, Mushrooms and Caramelized Onions

A savory, nutrient-packed vegetable skillet featuring golden caramelized onions, earthy mushrooms, and tender sautéed spinach.

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Prep Time 10 minutes mins

Cook Time 15 minutes mins

Total Time 25 minutes mins

Servings: 4 servings

Course: Side Dish, Vegetables

Cuisine: American, Healthy

Calories: 140

Ingredients

  

Vegetables

• 2 onions thinly sliced
• 8 oz mushrooms sliced
• 4 cups spinach fresh

Cooking Fats

• 2 tbsp olive oil
• 1 tbsp butter

Seasoning

• 3 cloves garlic minced
• 0.5 tsp salt
• 0.5 tsp black pepper
• 0.5 tsp thyme dried
• red pepper flakes optional

Finishing

• lemon juice squeeze for finishing
• fresh parsley optional garnish

Equipment

• Skillet
• Wooden spoon
• Cutting board
• Chef’s knife

Method

 

1. Heat olive oil and butter in a skillet over medium heat. Add sliced onions and cook 10–12 minutes until caramelized.
2. Add mushrooms and cook 5–7 minutes until browned.
3. Stir in garlic, salt, pepper, and thyme and cook 1 minute.
4. Add spinach in batches and sauté until wilted and tender.
5. Finish with a squeeze of lemon and garnish with parsley if desired.

Notes

Great as a topping for bowls, pasta, or toast.

Tips for Best Results

• Let onions caramelize fully — the flavor payoff is worth it.
• Don’t overcrowd mushrooms — give them space so they brown, not steam.
• Use fresh spinach — frozen spinach doesn’t give the same texture.
• Add garlic later to prevent burning.
• Finish with something acidic like lemon to brighten the dish.

Variations

• Add balsamic glaze for a sweet, tangy finish.
• Use kale instead of spinach for a sturdier green.
• Add cream & parmesan to turn it into a creamy skillet vegetable.
• Add chickpeas to make it a full vegetarian meal.
• Top with feta or goat cheese for Mediterranean flavor.

Serving Suggestions

This dish goes perfectly with:

• Grilled chicken
• Steak or pork chops
• Creamy mashed potatoes
• Rice and quinoa bowls
• Pasta
• Omelets and breakfast skillets
• Toast with ricotta or cream cheese

Fun Fact

Caramelized onions are not just “fried onions” — they undergo a slow Maillard reaction that transforms natural sugars into rich, deep, savory sweetness.