Pat the chicken breast dry with a paper towel and season both sides with sea salt, black pepper, dried oregano, and half of the lemon zest.
Preheat a grill or grill pan over medium-high heat and lightly coat with a tiny bit of oil to prevent sticking.
Grill the chicken for 6-7 minutes per side, or until the internal temperature reaches 165°F, then set aside to rest for 5 minutes before slicing.
In a small bowl, whisk together the extra virgin olive oil, fresh lemon juice, and the remaining lemon zest to create the dressing.
Place the mixed baby greens in a large bowl and toss gently with half of the prepared dressing.
Top the greens with sliced strawberries, blueberries, and the sliced avocado.
Slice the grilled chicken into strips and place it on top of the salad.
Drizzle the remaining dressing over the chicken and fruit, and serve immediately.