Season the chicken breast evenly with sea salt, black pepper, and dried oregano on both sides.
Heat half of the olive oil in a skillet or grill pan over medium-high heat and sear the chicken for 6 minutes per side until fully cooked.
Transfer the chicken to a cutting board and let it rest for 5 minutes before slicing into thin strips.
In a small bowl or jar, whisk together the remaining olive oil, lemon juice, honey, and Dijon mustard until the dressing is emulsified.
Slice the cucumber into thin half-moons and cut the cherry tomatoes into halves.
Place the mixed greens in a large serving bowl and arrange the cucumber, tomatoes, and sliced avocado on top.
Add the sliced chicken strips to the bowl and drizzle the lemon-herb vinaigrette over the entire salad.
Garnish with chopped fresh parsley and serve immediately for a bright and nutrient-dense meal.