Over medium-high heat, heat 2 tablespoons of olive oil in pan. Saute onions until translucent.
Stir in farro and toast for 1-2 minutes.
Add broth and bring to a boil. Once boiling, lower heat and cover pan with a lid.
Allow farro to simmer for 20-30 minutes until liquid has absorbed and the farro is tender. Drain any extra liquid that remains and allow to cool to room temperature.
While farro cools make the vinaigrette by whisking together 3 tablespoons of olive oil, the dijon mustard and red wine vinegar.
In a large bowl, lightly toss together the cooled and drained farro, vegetables, herbs, feta cheese, and vinaigrette.
Serve immediately or let marinate further in fridge until meal time.