In a bowl, combine 2 tbs olive oil, 1 tbs lemon juice, 1 tsp minced garlic, 1 tsp dried oregano, 1 tsp salt, and 1/2 tsp black pepper. Add the chicken, coat well, and let sit at room temperature for 15 minutes or refrigerate for up to 2 hours.

Grill chicken

Preheat a grill or grill pan to medium-high (about 400°F / 200°C). Grill chicken 4–6 minutes per side, or until internal temperature reaches 165°F (74°C). Remove from heat and let rest 5 minutes, then slice chicken thinly across the grain.

Prepare vegetables

While chicken rests, wash and dry the lettuce and tear or chop into bite-sized pieces to yield about 4 cups. Peel and shred or julienne 1 cup of carrot. Trim and thinly slice 2 celery stalks (about 1 cup when sliced). Thinly slice or shred 1 cup red cabbage. Halve 1 cup cherry tomatoes. Slice 1 cup pitted black olives if not pre-sliced. If using small mozzarella balls, drain and halve any large ones to total 1 cup.

Assemble salad

On a large platter or in a bowl, arrange the lettuce as a base. Scatter carrots, celery, red cabbage, cherry tomatoes, black olives, and mozzarella evenly over the lettuce. Top with the sliced grilled chicken.

Dressing

Make vinaigrette by whisking together 3 tbs extra-virgin olive oil, 1 tbs red wine vinegar, 1 tsp Dijon mustard, 1/2 tsp honey (or maple syrup), 1/2 tsp salt, and 1/4 tsp black pepper until emulsified. Taste and adjust seasoning.

Just before serving, drizzle the vinaigrette over the assembled salad (start with about 2/3 of the dressing) and toss gently to combine, or serve the dressing on the side. Add more dressing to taste.