Place the chicken broth, rice, celery, and 1 cup of chopped onion into a large pot. Bring to a boil over high heat. Reduce heat to medium-low, cover, and simmer until the rice is tender, 20 to 25 minutes.
Meanwhile, place the remaining 1/2 cup of onion into a large skillet along with the garlic, pork sausage, and ground beef. Cook and stir over medium-high heat until the meat is brown and crumbly; pour off excess grease, then stir the meat into the cooked rice along with the thyme, parsley, and oregano. Stir well.
