Preheat oven to 400 degrees
Combine olive oil, lemon juice, lemon zest, garlic, oregano, salt, and black pepper in a bowl.
Place chicken breasts into a 9x13-inch baking dish.
Brush lemon juice mixture over chicken
Place potatoes, red bell pepper strips, red onion, and lemon slices in a bowl, pour remaining lemon juice mixture over vegetables, and toss to coat.
Arrange vegetables and lemon slices around chicken breasts in baking dish.
Bake in the preheated oven for 30 minutes; brush chicken and vegetables with pan drippings.
Continue baking until chicken is browned, the juices run clear, and an instant-read meat thermometer inserted into the thickest part of a breast reads at least 160 degrees about 30 more minutes.