Heat the oil in a large saute pan over medium heat. Add the onion and garlic and saute until cooked. Add the wine and reduce by half, then add the plum tomatoes, oregano and parsley. Add the mussels to the pan and allow to cook for about 10 minutes until all the mussels are open. Transfer mussels to a platter. (Discard any mussels that do not open.)
You can mound some pasta in the center of the plate surrounded by the mussels or have some bruschetta handy for dipping into the sauce.
Adjust the seasoning for the sauce with salt and pepper, as necessary. Coat the mussels with the sauce and sprinkle with fresh chopped basil just before serving.