Preheat your oven to 400°F and line a small baking sheet with parchment paper.
Pat the chicken breast dry and rub with 0.5 tablespoon of olive oil, dried oregano, sea salt, and black pepper.
Place the chicken on the baking sheet and bake for 20 to 25 minutes, or until the internal temperature reaches 165°F.
While the chicken is baking, halve the cherry tomatoes, slice the cucumber into rounds, and dice the avocado.
In a large salad bowl, combine the mixed greens, tomatoes, and cucumber.
Whisk together the remaining 0.5 tablespoon of olive oil and the lemon juice to create a light dressing.
Once the chicken is cooked, let it rest for 5 minutes before slicing it into thin strips.
Toss the greens with the dressing, top with the sliced chicken and avocado, and serve immediately.