Heat a 5- quart dutch oven over medium-high heat. Add in the vegetable broth, olive oil, oregano, red pepper flakes, salt, and pepper. Bring to a boil.
Add in the orzo pasta and tomatoes. Reduce heat to medium and cook for 20-25 minutes, until the pasta is tender, stirring occasionally.
Remove the pot from the heat and add in the cubed feta cheese and red wine vinegar (or lemon juice). Stir to combine. Adjust seasonings if necessary.
Serve warm.
