Mix together oil, vinegar, oregano, all purpose seasoning, salt and black pepper. Combine with sirloin and mix to coat the sirloin beef.

Place in the fridge for at least 2 hours.

In a pot over high heat, add about 1 tbsp olive oil. When oil is hot, brown the beef on both sides then place onto a plate.

Add onion to the pot and cook for about 10 minutes until it begins to brown.

Add browned sirloin beef and juices back to the pot and add enough water to cover.

Bring to a boil then reduce to simmer and cover pot. Cook until beef is tender and sauce has reduced and thickened. Add more water as needed as it cooks. Remove from heat and serve with rice.