In a saucepan over medium heat, combine vinegar, salt, brown sugar, oregano, garlic cloves and olive oil and bring to a simmer. Add sliced peppers and simmer for 10 to 15 minutes until the peppers are tender.Transfer peppers into a pint mason jar and pour the liquid over top; secure with airtight lid and refrigerate overnight to let flavors infuse. Peppers will keep in the refrigerator for up to 1 month.