In a large skillet, heat oil over medium-high.
Add the meat, salt & pepper to taste, and cook until browned - about 10 minutes.
Remove meat from pan, and set aside. Lower heat to medium and saute the onions, about 3 minutes. Add the oregano and garlic and cook for 3 more minutes.
Add tomato paste, stir, cook for 3 more minutes.
Add the vinegar, stir, then add the meat back in. Combine meat mixture well.