Whisk the vinegar, mustard, garlic, oregano, salt, and black pepper in a small bowl. Whisk in oil. Set dressing aside.
Rinse farro in cold water. Cook according to package instructions. In a colander, drain off any excess water, and rinse the grains quickly in warm water. Transfer the warm grains to a large bowl and toss with 3 Tbs. of the dressing. Let cool.
Add tomatoes, chickpeas, olives, cheese, salami, and red pepper. Pour in the remaining dressing and toss to coat. Fold in basil.