Season the chicken breast with sea salt, black pepper, and dried oregano.
Grill the chicken over medium-high heat for approximately 6 minutes per side until the internal temperature reaches 165°F.
While the chicken is grilling, chop the romaine lettuce, cucumber, red bell pepper, and radishes into bite-sized pieces.
Prepare the dressing by whisking together the extra virgin olive oil, fresh lemon juice, and Dijon mustard in a small bowl.
In a large mixing bowl, toss the chopped vegetables and shredded carrots with half of the prepared dressing.
Slice the grilled chicken into thin strips once it has rested for 3 minutes.
Arrange the salad on a plate, top with the sliced chicken and fresh avocado, and drizzle with the remaining dressing.