Using a knife, slice off 1/4 to 1/2 inch from the top of unpeeled garlic head to expose cloves. Place garlic in a small dish and drizzle with 1/2 tsp oil. Cover with foil, then bake in oven until garlic feels soft when pressed, 25 - 35 minutes. Remove from oven and cool. The recipe only calls for 5 - 6 cloves. Use the rest for other dishes.
Mash 6 cloves with a fork. Stir in oregano, salt and pepper. Whisk in remaining oil, vinegar and enough water for a dressing consistency. Stir in sun-dried tomatoes. Taste and add additional salt if needed.
In a large bowl, toss lettuce with tomatoes and cucmber. Toss with dressing. Add olives and cheese and toss again.