Follow these steps to create mouth-watering Grilled Portobello Mushroom Burgers:

1. Clean Mushrooms: Rinse the Portobello mushrooms under cold water and use a paper towel to wipe off any excess moisture. Remove the stems gently.
2. Prepare Marinade: In a medium bowl, combine balsamic vinegar, olive oil, minced garlic, dried oregano, salt, and black pepper. Whisk well.
3. Marinate Mushrooms: Place the mushrooms in a shallow dish. Pour the marinade over them, ensuring they are well-coated. Let the mushrooms sit for 30 minutes to absorb the flavors.
4. Preheat Grill: Preheat your grill to medium-high heat.
5. Grill Mushrooms: Place the marinated Portobello mushrooms on the grill, gill side down. Grill for about 5-7 minutes before flipping.
6. Add Toppings: If using cheese, add a slice on top of the mushrooms during the last minute of grilling to let it melt.
7. Grill Buns: Toast the burger buns on the grill for 1-2 minutes until golden brown.
8. Assemble Burgers: Remove the mushrooms from the grill and place them on the bottom half of the toasted burger buns.
9. Add Fresh Ingredients: Top with leafy greens, sliced tomatoes, red onion, and avocado slices.
10. Finish Up: Place the top half of the burger bun over everything. Serve warm alongside your favorite sides.

Congratulations! You’ve made delicious Grilled Portobello Mushroom Burgers that are sure to impress.