1. Mix olive oil, lemon juice, and salt in a small mixing bowl. Set aside.
2. Chop apple into ½ inch pieces, set aside.
3. Set up 4 meal prep containers next to each other. Pile 2 cups greens into each meal prep container, then divide apple, chicken, cheese, red onions, and walnuts between containers. Place a slice of bread in container or in a separate bag.
4. Place 4 small salad dressing containers on the table and divide mixed salad dressing between the containers. Place the lid on top. Refrigerate for up to 4 days. Toast bread prior to eating.