Cut roast across grain into 1/16-inch strips. Combine 2 T. olive oil, soy sauce, and next 3 ingredients in a large zip-top plastic freezer bag. Seal bag; shake to blend. Add beef to bag; seal and turn to coat. Chill 1 hour.
Remove beef from marinade, reserving marinade. Heat 2 T. olive oil in large skillet over medium-high heat. Increase heat to high. Add beef to skillet; cook 2 to 3 minutes or until browned, stirring often. Stir reserved marinade into beef; cover, reduce heat to low, and simmer 17-20 minutes or until tender, stirring occasionally.
Meanwhile, heat remaining 1 T. olive oil in a large nonstick skillet over medium high heat. Add green bell pepper and next 4 ingredients. Cook, stirring often, 3 to 4 minutes or until vegetables are crisp-tender. Remove from heat.
Combine cornstarch and broth, stirring until smooth. Stir cornstarch mixture into beef mixture. Stir in vegetable mixture and tomatoes. Serve immediately over rice, soft polenta, or gnocchi. Garnish if desired.