Meaty grilled portobello mushrooms with a savory marinade are a healthy, vegetarian, high protein alternative for the grill. This keto-friendly, clean eats option is perfect for plant-based family meals.
Wipe the portobello mushroom caps clean with a damp paper towel and gently remove stems.
In a small bowl, whisk together olive oil, balsamic vinegar, minced garlic, salt, black pepper, and dried thyme until fully emulsified.
Brush both sides of each mushroom generously with the marinade, ensuring to get some marinade under the gills as well; let marinate for at least 15 minutes.
Preheat grill or grill pan to medium-high heat (about 400°F); oil grates lightly to prevent sticking.
Grill mushrooms gill-side down first for 4–5 minutes, then flip and cook another 4–5 minutes, pressing gently to ensure even contact with the grill. Mushrooms should be nicely charred but still juicy.
Transfer to a plate, let rest 2 minutes, and serve immediately as steaks or burger patties.