In a small bowl, whisk together the olive oil, lemon juice, minced garlic, dried oregano and pepper.
Place the chicken breasts, drained diced tomatoes, green olives and capers (optional) in the base of the multi-cooker insert and pour the olive oil sauce over the top.
SLOW COOKER: Set SLOW COOKER on low and cook for 8 hours.
BAKED: Set OVEN to 350 F for 55 minutes. Cook until chicken is no longer pink.
Cook the rice, for side dish.
Prepare salad.
Serve Multi-Cooker Greek Chicken with crumbed feta cheese garnish, over rice with salad.