Place oxtails in a heavy soup kettle or dutch oven. Add soy sauce, oyster sauce, and liquor. Cover and marinate for one hour.
Cook covered over medium heat for 30 minutes to draw out juices.
Uncover. Bring to a boil and turn often till meat is browned and liquid is evaporated. Add garlic, bay leaves, oregano, and one onion, coarsely chopped, along with 1/4 cup beef broth. Cook and stir to deglaze pan.
Add remaining beef broth. Cover and simmer gently until meat is tender when piereced (about 3 hours).
Remove pan from heat. Strain broth into a large saucepan or bowl. Discard onion and herbs; set meat aside. When meat is cool, remove it from bones, cut in bite-sized pieces, and return to broth. Refrigerate several hours or overnight.
Skim off and discard fat. Bring broth to a boil. Add celery, carrot, and 2 medium onions, coarsely chopped. Reduce heat, cover, and simmer until veggies are tender (about 20 minutes).