Trim fat from steak. Slice steak diagonally across grain into 1/4-inch-thick strips. Cut strips into 2-inch pieces; set aside.
Add oil to a large nonstick skillet, and place over medium-high heat until hot. Add meat, garlic, and next 3 ingredients; cook 4 minutes, stirring often. Remove from pan, and set aside.
Add bell pepper strips to pan; cook 6 minutes or until tender, stirring often. Return meat to pan, and add vinegar. Cook 2 minutes or until thoroughly heated. Spoon meat mixture over rice.