Remove mushrooms (4) stems. Option to remove mushrooms gills by scooping them out with a spoon. Brush the caps of the mushrooms with a paper towel to clean them.
Brush both sides of the mushrooms with olive oil (3 tablespoons). Feel free to use more olive oil, as mushroom sizes will vary. In a small mixing bowl combine the salt (1/2 teaspoon), pepper (1/4 teaspoon), and garlic powder (2 teaspoons). Sprinkle evenly over both sides.
Light the grill and heat to medium-high. Grease the grates, and place the mushrooms cap side down. Cook until the mushrooms begin to soften--about 5 minutes. Flip and grill on the stem side for about 3-5 minutes, or until the mushrooms have softened to your liking.
If you're using any of the optional toppings, sprinkle on top before serving, and enjoy!