Place lettuce in the bottom of a shallow 4 quart bowl (preferably glass- so guests can see all the layers). Add layers of onion, cucumber, tomatoes and peas.
Blend mayonnaise, sugar, parmesan, salt and garlic powder. Spread mixture evenly over the top layer of veggies. Cover and chill as long as 24 hours. Just before serving - sprinkle with eggs and bacon. Serve with salad tongs to ensure that you include all layers and dressing.