Heat oil in large saucepan or Dutch oven on medium-high heat. Add 1/2 of the meat. Brown on all sides. Remove with slotted spoon. Repeat with remaining meat and the onion.
Return all meat to saucepan. Stir in beef broth, tomatoes, mushrooms, carrots, 1/2 cup water, oregano, garlic powder, thyme, pepper and bay leaf. Bring to boil. Reduce heat to low; cover and simmer 1 hour or until meat is tender.
Mix cornstarch and 4 teaspoons water in small bowl. Add to saucepan along with rice. Bring to boil on medium-high heat. Reduce heat to low; cook and stir 4 minutes or until slightly thick and rice is tender. Discard bay leaf.