In a small bowl, whisk together oil, lemon juice, garlic and Italian seasoning.
Season to taste. Add chicken and toss to coat evenly.
Heat a non-stick frying pan. Add chicken in an even layer and cook undisturbed for 4 minutes. Flip and cook for an additional 3 minutes, until the chicken is cooked through. Remove chicken to a plate and set aside.
In the same pan, reduce heat to medium and add the capsicum. Season with pepper and sauté for 10 minutes, or until tender, stirring occasionally. If required, add a splash of water to the pan.
Once vegetables are tender, add chicken and remaining juices back into the pan, gently stirring to combine and reheat the chicken.
Place mixed salad greens on a plate and serve with the chicken and vegetables.