Chopped fresh herbs: any mix of basilparsley, or thyme, optional for serving (I used fresh thyme)
Lightly coat a 5-quart or larger slow cooker with nonstick spray. Heat the oil in a large skillet over medium high. Sprinkle the chicken with salt and pepper, then place it in the hot pan, seasoned side down. Let brown on the first side for 1 to 2 minutes until golden, then flip and brown on the other side for 1 additional minute. If your skillet isn’t large enough to fit all of the chicken pieces, work in batches so that the chicken does not overlap. Transfer the chicken to the slow cooker.
Arrange the peppers, olives, and onions around the chicken (do not place on top).
In a small bowl or measuring cup, whisk together the red wine vinegar, garlic, honey, oregano, and thyme. Pour over the chicken and vegetables. Cover and cook for 1 1/2 to 2 hours on high or 3 to 4 hours on low, until the chicken is cooked through and the center reaches 165 degrees F. Serve warm, sprinkled with feta and fresh herbs.
All slow cookers differ in temperature and cooking times, so adjust the cooking time according to your experience with your model. When in doubt, check early to ensure the chicken does not overcook.
Store leftovers in the refrigerator for up to 4 days. Since chicken can be hard to reheat, I recommend cutting it into smaller pieces, then reheating gently in the microwave with a splash of chicken stock. You can also enjoy leftover chicken at room temperature over salads or try mixing it into hot pasta.