In a large 6-qt. stockpot, heat oil over medium-high heat. Add onion and cook until tender, 4-5 minutes. Add garlic, and cook 1 minute longer or until fragrant.
Add chicken broth and bring to a boil. Add celery, carrots, bay leaves, and thyme to the pot. Reduce the heat to a simmer, uncovered, 25-30 minutes.
Remove the pot from heat. Add the noodles. Let stand, covered, until the noodles are tender, 20-22 minutes.
Stir in the parsley and lemon juice. Discard the bay leaves. Add additional salt and pepper if desired.