Boil pasta in salted water, according to directions, until al dente.
In a large frying pan, heat 2 tablespoons butter over medium-high heat. Swirl the pan and add the tilapia pieces. Sprinkle with the greek seasoning and allow fish to brown lightly, turning, for about 5 minutes. Remove fish and place in a bowl and set aside. Note: it should be a bit undercooked in the middle as it will continue to cook while it rests.
Add the remaining 2 tablespoons butter to the frying pan and turn the heat to medium. Add the garlic and olives and stir until the butter begins to bubble about 1 minute. Turn down to medium-low and add the yogurt and stir to combine. Using a spider or slotted spoon, remove the pasta from the water, draining as much as possible, and add to the yogurt mixture. Toss to coat in sauce. Add the fish pieces and any accumulated juice. Sprinkle with feta and parsley and serve immediately.
Recipe by Farmgirl Gourmet at http://www.farmgirlgourmet.com/2014/01/pasta-tilapia-olives-feta.html