Warm the olive oil in a large saucepan over medium heat. Add the onion and cook, occasionally stirring, for 5-6 minutes, until translucent. Add the garlic and cook for another minute.
Add the vegetable broth, diced tomatoes, tomato sauce, oregano, and thyme. Season with salt and pepper. Taste broth and adjust seasonings if needed.
Bring to a simmer. Add the tortellini and cook according to package directions. Stir in the spinach during the last minute of cooking.