Combine the chicken, potatoes, feta cheese, olives, lemon juice, olive oil, dried oregano, salt and black pepper in a Medium Ziploc® brand Zip'n Steam® Bag.
Seal bag and shake gently to combine ingredients. Pat ingredients into single layer. Place bag in microwave.
Cook on full power 7 - 7 1/2 minutes (Medium bag) or 6 - 6 1/2 minutes (Large bag), until chicken is cooked through, with no trace of pink. If needed, continue microwaving at 30-second intervals until chicken is done.
Allow bag to stand 1 minute before handling. Gently shake bag to distribute seasonings. Carefully open bag.
Garnish with additional 1/4 cup (1 ounce) crumbled feta and 1 Tablespoon chopped fresh oregano, if desired. Serve with pita bread.