First make the dressing. Put the red wine vinegar, lemon juice, oregano, pickling liquid, water and salt and pepper into a bowl and mix. Set aside.
Arrange the mixed leaves on a plate or in a bowl, then arrange the tomatoes, cucumber and red onions on top. Drizzle the salad with a couple of tablespoons of the dressing. Top with the diced cheese.
Serve with the remaining dressing on the side.