Grilled Portobello Burgers
Meaty portobello caps marinate in balsamic and garlic, then grill until tender and juicy with deep char marks, standing in beautifully for a beef patty. Stacked with melted provolone, caramelized onions, and arugula on a toasted bun, it's a hearty vegetarian burger that satisfies everyone at the cookout.
By YumYum Editorial · BBQ & Grilling
Prep: 15 min · Cook: 12 min · Total: 27 min · Serves 4
Ingredients
- 4 large portobello mushroom caps, stems and gills removed
- 1/3 cup balsamic vinegar
- 3 tbsp olive oil, divided
- 2 cloves garlic, minced
- 1 tsp fresh thyme leaves
- 1/2 tsp kosher salt
- 1/4 tsp black pepper
- 1 large yellow onion, thinly sliced
- 4 slices provolone or smoked gouda
- 4 burger buns, toasted
- 1 cup baby arugula
- to taste Mayonnaise or aioli, for spreading
Instructions
- Clean the portobello caps with a damp paper towel and scrape out the dark gills with a spoon to prevent a muddy, watery texture.
- Whisk together balsamic vinegar, 2 tbsp olive oil, garlic, thyme, salt, and pepper. Pour over the mushroom caps and marinate 30 minutes, turning once.
- Meanwhile, heat the remaining 1 tbsp olive oil in a skillet over medium-low heat. Add sliced onion and cook slowly, stirring occasionally, for 20-25 minutes until deeply caramelized.
- Preheat the grill to medium heat, about 375-400°F.
- Grill the marinated mushroom caps gill-side down for 5-6 minutes, then flip and cook 4-5 minutes more until tender and grill-marked, basting with leftover marinade.
- During the last 2 minutes, top each mushroom with a slice of cheese and close the grill lid to melt it.
- Spread toasted buns with mayonnaise or aioli, then layer with arugula, the cheesy mushroom cap, and a generous pile of caramelized onions.
- Serve immediately while the cheese is still melty and the mushroom is warm.