Grilled portobello mushroom burgers layered with grilled eggplant, roasted red peppers, red onion, arugula, and basil pesto make an exceptionally flavorful meatless burger.

The Ultimate Grilled Portobello Burger

One evening I wanted all the satisfaction of a veggie burger without spending time forming patties or dealing with ingredients that fall apart. The solution was obvious: don’t make a patty. Build a burger from boldly seasoned and grilled vegetables. The result is a textured, juicy sandwich that showcases the vegetables rather than masking them.

I grilled portobello mushroom caps and slices of eggplant, layered them with roasted red bell pepper, thinly sliced red onion, fresh arugula, and a bright basil pesto. I finished the burger on toasted buns with melted Havarti cheese for a creamy, slightly tangy contrast. This combo is simple, fast, and genuinely satisfying—perfect for weeknights or a weekend cookout.

This grilled portobello burger is adaptable. Use store-bought roasted peppers or roast your own. Swap Havarti for another melting cheese or skip cheese for a dairy-free option. You can grill or caramelize the onions if you prefer a sweeter note. Add grilled asparagus, sweet potato slices, or sun-dried tomatoes for extra depth. A drizzle of reduced balsamic or a spicy aioli are excellent alternate sauces, while baby spinach can replace arugula for a milder green. The recipe below reflects the original combination, but feel free to make it your own.

Why this veggie burger works

Using whole vegetables as the “patty” keeps the flavors clean and unmistakable: smoky grill marks on the eggplant, meaty texture from the portobello, sweet roasted pepper, and peppery arugula. The balsamic-olive oil marinade lifts the mushrooms, while pesto adds herbaceous richness. Toasting the bun with cheese ties the elements together and gives you the pull-and-go comfort of a traditional burger.

Ingredients

2 large portobello mushroom caps
3 tablespoons olive oil
3 tablespoons balsamic vinegar
Pinch sea salt
1 small eggplant, cut into 1/4- to 1/2-inch rounds
1 roasted red bell pepper (store-bought or homemade)
1/4 small red onion, thinly sliced
1/4 cup basil pesto
Handful baby arugula
2 burger buns of choice, toasted
2 slices Havarti cheese (or alternative of choice)

Instructions

Combine the olive oil and balsamic vinegar in a small container and whisk until combined. Wipe the portobello caps clean, place them in a sealable bag or container, and pour in the balsamic marinade. Let the mushrooms marinate for at least 15 minutes and up to 1 hour.
Preheat a grill to medium heat. Brush the eggplant slices lightly with olive oil and season with salt and pepper.
Place the portobello caps and eggplant slices on the hot grill. Cover and cook until grill marks appear: about 2–3 minutes per side for the eggplant and about 5–7 minutes per side for the mushrooms, until both are tender and cooked through. Transfer to a plate when done.
Toast the burger buns and melt Havarti on the buns if desired. Build each burger by layering a grilled portobello cap, a few eggplant slices, roasted red pepper, red onion, and arugula. Drizzle with pesto to taste and serve immediately.

Optional variations and tips

Try these ideas to customize your grilled portobello burger:

Swap pesto for a smoky chipotle aioli or a balsamic reduction for different flavor profiles.
Add sun-dried tomatoes or grilled sweet potato slices for extra texture.
Caramelize red onions on the grill or in a skillet for a sweeter element.
Use gluten-free buns, whole-grain rolls, or go bun-less and serve on a bed of greens.
For a vegan version, omit cheese and use a vegan pesto or spread.

Nutrition (approximate)

Serving: 1 burger. Calories: 668 kcal; Carbohydrates: 65 g; Protein: 32 g; Fat: 32 g; Fiber: 11 g; Sugar: 13 g. Nutrition values are approximate and should be used only as a guideline.

More veggie burger inspiration

If you enjoy meatless burgers, explore other recipes such as white bean or sweet potato patties, or beet-based burgers with Mediterranean spices and herbed cheese. These options highlight other plant-forward textures and flavors while offering satisfying, balanced meals.