Marinate the chicken: add the chicken, garlic, oregano, red wine vinegar, olive oil, prunes, olives, capers, bay leaves, salt and pepper to a large mixing bowl. Coat the chicken well. Transfer to a plastic baggie or just cover and refrigerate for at least 2 hours or up to 24 hours. Toss the chicken to get the marinade coated all over every few hours if you remember.
2 1/2 lbs. chicken thighs, skin on, bone-in, 8 cloves garlic, smashed (or more if preferred), 1/2 cup fresh oregano leaves, 1/3 cup red wine vinegar, 1/3 cup olive oil, 1 1/2 cups California prunes (you can keep whole or slice in half), 1 cup green olives, pitted (you can keep whole or slice in half), 1/3 cup capers plus 2 Tbsp. of their brine, 2 bay leaves, 1 Tbsp. kosher salt, freshly ground black pepper