Start by mixing lemon juice, Dijon mustard, red wine vinegar, sugar, minced shallot, oregano, parsley, olive oil, salt, and pepper. Divide the mixture, using half to marinate the chicken for at least one hour. The rest becomes your salad dressing. Marinating helps the chicken soak up flavor and stay juicy on the grill.
Preheat your grill to medium-high heat. Place the marinated chicken on the grill and cook about 5-6 minutes per side, depending on thickness. I like to let it rest for 5 minutes before slicing to lock in the juices and maintain tenderness.
In a large bowl, toss romaine lettuce with half of the reserved dressing. Arrange sliced chicken, tomatoes, corn, cucumber, red onion, bacon, blue cheese, and avocado over the top. Drizzle remaining dressing and serve immediately. It looks as good as it tastes!