Begin by preparing the dressing. Combine olive oil, red wine vinegar, Dijon mustard, oregano, lemon juice, minced garlic, salt, and pepper in a bowl and mix well.
Pour the dressing into the bottom of a Mason jar.
Next, layer in the ingredients: start with the chopped tomatoes, followed by the red onions, cucumbers, diced chicken breast, feta cheese, kalamata olives, and finally the chopped lettuce.
Make sure to cut all the ingredients into small, uniform pieces for the best presentation and flavor.
