3 pounds Yukon gold potatoes
3/4 teaspoon salt
1 (16-ounce) bottle olive oil-and-vinegar dressing, divided
8 cups mixed salad greens
2 large avocados
1 tablespoon fresh lemon juice
3 large tomatoes, seeded and diced
12 small green onions, sliced
2 cups (8 ounces) shredded sharp Cheddar cheese
4 ounces crumbled blue cheese
6 to 8 slices bacon, cooked and crumbled
Freshly ground pepper to taste
Cook potatoes in boiling salted water to cover 30 minutes or until tender. Drain and cool slightly. Peel and cut into cubes.
Sprinkle potatoes evenly with 3/4 teaspoon salt. Pour 1 cup dressing over potatoes; gently toss. Set aside remaining dressing. Cover potato mixture; chill at least 2 hours or overnight.
Arrange salad greens evenly on a large serving platter. Peel and chop avocados; toss with lemon juice.
Arrange potatoes, avocados, tomatoes, and next 4 ingredients in rows over salad greens. Sprinkle with pepper. Serve with remaining dressing.