In a bowl, toss the lemon with 1/2 tsp. salt. Let stand until softened, about 20 minutes. Meanwhile, in a large nonstick skillet, cook the potatoes in 1/2 cup water over medium-high heat, partially covered, until the liquid has nearly evaporated, about 5 minutes. Add 1 tbsp. EVOO and cook, stirring, until golden-brown, about 5 minutes. Remove from heat and stir in the parsley. Cover to keep warm.
In a large nonstick skillet, heat the remaining 2 tbsp. EVOO over medium-high. Season the chicken and add to the pan, skin side down. Cook, turning once, until browned, about 10 minutes. Transfer to a plate.
Discard all but 2 tbsp. fat from the pan. Reduce heat to medium. Add the garlic and lemon and cook, stirring, until golden-brown, 2 minutes. Stir in 2/3 cup water. Add the chicken and any juices and the oregano; cook, partially covered, turning chicken once, until cooked through, about 15 minutes. Stir in the potatoes, scallions and olives and cook 2 minutes.