Heat olive oil in large pot over medium heat.
Add onion and fennel. Cook 5 to 6 minutes until soft.
Add garlic. Cook 1 minute.
Add white wine. Simmer 2 minutes.
Add tomatoes, stock, bay leaf, oregano, and red pepper flakes.
Bring to boil. Reduce to medium-low. Simmer 15 minutes.
Season with salt and pepper.
Add fish. Cover. Simmer 3 minutes.
Add shrimp and scallops. Cover. Simmer 2 minutes.
Add mussels. Cover. Simmer 3 to 4 minutes until mussels open.
Discard unopened mussels. Remove bay leaf.
Serve with parsley, lemon wedges, and crusty bread.