1. Start the water for the pasta. In a large mixing bowl, combine feta, green onions, oregano, tomatoes with their juice, salt and pepper to taste and the olive oil. Let this mixture sit on the counter while you get the rest of the meal ready.
2. In a skillet, melt butter over medium heat. Add a dash of olive oil to keep the butter from burning. When hot, add the garlic and stir quickly. Now add the shrimp and toss together till the shrimp pinks up. Salt and pepper to taste; don't overcook. Meanwhile, your pot has boiled and your pasta should be cooking.
3. Once the pasta has cooked and been drained, add the shrimp mixture with cooked pasta and toss lightly. Add the feta mixture, lightly toss again and serve.