For the salad: Combine the lettuce, cucumbers, tomatoes and carrots in a bowl.
For the dressing: In a small bowl, stir to combine the mayo, sour cream, onion salt, garlic powder and white pepper. Lightly stir in the cheese until just combined. If the salad dressing to too thick, it can be thinned with a little milk.
Serve the salad on salad plates and drizzle dressing over top.
This recipe makes a large quantity of dressing. Store leftover dressing, covered, in the refrigerator for up to 2 weeks.