Preheat oven to 425°.
Rinse green beans in cool water, and pat dry with a paper towel.
Cut dried ends off of green beans.
Line a large cookie sheet with parchment paper.
Dump beans and olives onto the cookie sheet.
Drizzle with olive oil and vinegar, and sprinkle with oregano and salt and pepper.
Toss with a spoon and spread everything out.
Place the pepperoncinis on the cookie sheet.
Bake for 15-20 minutes checking for doneness at the 15-minute mark.
Crumble the feta cheese pieces and set aside while the beans are roasting.
When the beans are finished roasting, transfer them to a serving dish and sprinkle them with feta cheese.