1 In A Large Skillet Heat Olive Oil Over Medium High Heat. Add The Onions And Cook Until Tender, About 2-3 Minutes. Add The Garlic And Cook Until Fragrant, About A Minute More. Add Tomatoes, Mushrooms, Olives, Oregano, Salt, And Pepper. Bring Sauce To Boiling. 2 Gently Place The Fish Fillets In The Pan And Scoop Some Of The Sauce Over The Fillets. Return To Boiling. Reduce The Heat And Cover. Simmer For 8 To 10 Minutes Or Until Fish Flakes Easily When Tested With A Fork. With A Wide Spatula, Lift Fish From Skillet To A Serving Dish. Spoon Sauce Over Fish. Serve With Rice, And/Or Crusty Bread.