Preheat broiler. Cut off mushroom stems even with caps; discard stems. Brush or lightly rinse mushroom caps. Gently pat dry with paper towels. Place mushrooms, stem sides up, in a small shallow baking pan. Set aside.
In a small bowl combine the crushed red pepper (if desired), seasoned salt, and garlic. Sprinkle evenly over mushrooms. Drizzle olive oil evenly over mushrooms.
Place mushrooms on the unheated rack of a broiler pan. Broil 3 to 4 inches from the heat for 8 to 10 minutes or until tender. Sprinkle with basil. Cut mushrooms in half; serve immediately.