In a large skillet, brown ground beef, drain grease, and set aside.
In the same pan, add 1-2 tablespoons olive oil over medium heat. Add the onions and thyme and cook until onions are soft and translucent, about 3-4 minutes. Add the garlic and cook for 1 minute. Add the ground beef, bell pepper, jalapeño pepper, tomatoes, Worcestershire sauce, salt, pepper, beef stock, and rice and stir to combine. Bring to a boil, reduce heat to low, then cover with lid and simmer for 15 minutes.