Preheat the oven to 400 degrees F.
Throw together your marinade/dressing by whisking together the balsamic vinegar, olive oil, dijon, salt, garlic and oregano.
Season your chicken with salt and pepper and place in a baking dish.
Pour 1/4 cup of the marinade over the chicken breasts (if you have the time, you can let the chicken marinade for a little) reserve the rest of the marinade for salad dressing.
Bake the chicken uncovered for 20-22 minutes - or until cooked through.
Assemble your salad with spring mix, tomatoes, mozzarella, cucumbers, red onion, and avocado. Slice your chicken breasts and place that on top, with some basil ribbons. Pour desired amount of remaining dressing over the salad. Enjoy!