In a large skillet, heat the olive oil over medium-high heat. Add the beef cubes and brown on all sides, about 5-7 minutes. Remove the beef and set aside.
In the same skillet, add the diced onion and garlic. Sauté until the onion is translucent, about 3-4 minutes.
In a slow cooker, combine the browned beef, sautéed onion and garlic, carrots, potatoes, red bell pepper, diced tomatoes, beef broth, Worcestershire sauce, thyme, oregano, salt, and pepper.
Stir everything together until well mixed. Cover and cook on low for 7-8 hours or on high for 4-5 hours, until the beef is tender.
Once cooked, taste and adjust seasoning if necessary. Serve hot, garnished with fresh parsley.