To make the chicken: Place the chicken breasts in a slow cooker. In a small bowl, combine the onion, garlic, oregano, salt, pepper, olive oil, red wine vinegar, lemon juice, and water.
To make the potatoes: Preheat the oven to 375 degrees F. Place the mini potatoes, olive oil, minced garlic, salt and pepper in a large bowl and toss to combine.