Lay your lettuce leaves on a large oval platter or a large, rimmed jelly roll pan. (The platter I used in the photos is about 14" x 18", but I've also made this salad on a 12" x 17" jelly roll pan.) Position longer, larger leaves at the bottom of the platter, leaving a little room to nestle the red pepper "presents" at the very bottom. Place progressively smaller and smaller leaves on the platter as you work toward the top of the platter, so it resembles the cone-shape of a Christmas tree.
As you layer on your lettuce, sprinkle a little of the chicken, avocado, eggs, bacon, and red onion throughout the layers, making sure you have plenty left to sprinkle on top. (Reserve the avocado until the last minute, though, if you're making this salad ahead of time – see note on make-ahead tips.)
Place the tomato halves, cut-side down on top of the salad, positioned to resemble ornaments.
Sprinkle the blue cheese on top to resemble snow. (Alternately, you can serve the blue cheese on the side if all of your guests don't like blue cheese.)
Cut the largest, flattest side off of the yellow pepper and use a star-shaped cookie cutter to cut out a star and place it at the top of your Christmas tree.
Using a sharp knife or cookie cutters, cut squares and rectangles out of the broad sides of the red peppers. Slice very thin strips of American cheese to lay on top of the peppers as ribbon. (If the cheese isn't adhering well to the peppers, very slightly dampening it on one side can help. Or, you can just barely soften it by placing the cheese-topped peppers in the microwave for maybe 10 seconds, so that the cheese softens just enough to stick better – but be careful not to heat it for so long that it loses its shape.) Place the presents at the bottom of the tree.
Serve with Italian Red Wine Vinaigrette Dressing, or your dressing of choice.
Purchased chicken, hard-boiled eggs, bacon, and onion: Depending on how much time you have to make this salad, you can choose to prepare and cook these items yourself, or purchase pre-cooked at the store. If purchasing pre-cooked bacon bits, be sure to use real bacon, rather than Bac-Os, and look for reduced-fat, leaner options (such as Hormel's reduced-fat bacon pieces), if possible. To save time during the holidays, you can also typically find diced hard-boiled eggs and red onion in the dairy and produce sections, or on the salad bar at most larger grocery stores.
Dressing options: Red wine vinaigrette is a classic choice for dressing Cobb salads, and we love the Italian flavor and sharp tang of our dressing, with the other flavors of the salad. Feel free, however, to use other dressing varieties that you like (trying to stick with organic, homemade, or Greek yogurt-based options if possible).
Make-ahead tips: You can completely assemble the salad (except the avocado) earlier in the day, or the night before. Wrap your salad platter with plastic wrap to prevent the lettuce from wilting (but be careful not to smash the lettuce by wrapping too tightly), and store in the refrigerator. Because avocado oxidizes and turns brown after cutting, we recommend that you sprinkle the avocado on at the last minute, or dice it just before serving and offer it in a bowl alongside. The dressing can be made up to several days in advance. However, it doesn't emulsify as completely as most of our other vinaigrettes, so you'll need to re-whisk it before serving.
Adaptations for vegetarians or for food preferences: I've also served this in a vegetarian version, omitting the bacon and chicken. If you'd like, you can serve certain toppings in a bowl off to the side, so that each guest can add the meat toppings (or toppings such as the blue cheese) only if they choose to do so. The most important things in making this look like a Christmas tree are the tomato "ornaments" and the pepper "star." The other toppings can be adjusted somewhat to accommodate personal preferences. Similarly, you can add more or less of certain toppings, depending on which you like best.
Adjusting the amount this salad serves: I've also made this salad double in yield, to serve at a larger holiday party. It's easy to do this by layering the lettuce more thickly, and increasing the amount of toppings and dressing.
Gluten-free tips: Although the ingredients used in this salad are all generally gluten free, there are a few items you may need to be careful with, when purchasing. Bacon, purchased rotisserie chicken, and dijon mustard usually don't contain gluten, but some brands may use seasonings that do have gluten, so be sure to read the labels carefully or look for gluten-free labeling, if needed. You can read more about purchasing gluten-free rotisserie chicken HERE, and about gluten-free mustard HERE.