Wipe the portobello mushroom caps clean with a damp paper towel.
In a small bowl, combine the olive oil, Worcestershire or soy sauce, garlic, salt, and pepper. Brush the mushrooms on both sides with the basting sauce. Sprinkle the mushrooms with a bit of additional salt.
Preheat the grill to medium-high. Grill the mushrooms for about 4 to 5 minutes total per side, turning them as needed so that they brown nicely and evenly. Baste with the remaining marinade as they cook.
Serve hot, warm, or at room temperature.
Notes
The mushrooms are just plain delicious on their own but also can be paired with a sauce for even more flavor. You can also serve them on a bun as a kind of mushroom burger, with or without a sauce or condiments. Some lettuce, onion, and a slice of tomato will make it feel even more like a burger!