Cook the pasta according to package directions, reserving 1/4 cup of the cooking water. Drain and set aside.
Into a large skillet over medium-high heat, add the olive oil. When the oil is hot, add the onion. Saute for 2 minutes, until softened. Add the garlic and continue cooking for an additional 30 seconds.
Add the peppers and cook, stirring frequently for 3 minutes, until crisp-tender. Stir in olives, oregano, salt, and pepper.
Add the cooked pasta and reserved cooking water, stirring gently to coat the pasta. Remove from heat.
Stir in feta cheese, adjust seasoning to taste, and serve warm.