Preheat oven to 450° F.
Place mussels in a large saucepan.
Add 2 cups water, cover, and steam mussels open.
Drain and allow to cool.
Remove mussels from shells.
Place 2 or 3 mussels in one shell until all mussels have been used.
In a small bowl combine tomatoes, bread crumbs, and parsley.
Place a small amount over mussels; drizzle with a little oil.
Arrange shells in a baking dish and bake about 5 minutes, or until slightly browned.