1. Preheat broiler.
2. To prepare tartines, place bread slices in a single layer on a baking sheet. Arrange 1 ham slice and 1 cheese slice on each bread slice. Broil 3 minutes or until cheese melts. Sprinkle evenly with 1 teaspoon oregano.
3. To prepare salad, combine 1 tablespoon oregano and next 4 ingredients (through garlic) in a bowl, stirring well with a whisk. Arrange 1 cup lettuce on each of 4 plates. Top each serving with 3/4 cup honeydew and 1/2 cup tomato slices. Drizzle each serving with about 1 tablespoon dressing. Place 1 tartine on each plate.