In a pot over medium-high heat, heat the olive oil. Add the ground beef and cook until browned, breaking it into crumbles. Drain any excess fat.
Transfer the beef to a 7-quart slow cooker. Add onions, carrots, celery, broth, tomato sauce, beans, seasonings, and crushed tomatoes. Stir to combine and adjust the seasonings to taste.
Cover and cook on high for 3 ½ hours.
Add the uncooked orzo pasta, stir, and continue to cook for an additional 30 minutes or until the pasta is al dente.
Garnish with Parmesan cheese and parsley, if desired.
Store orzo and soup separately in airtight containers in the refrigerator for up to 3 days.
Notes
- Add an extra 1-2 cups of broth as needed to achieve your preferred soup consistency.