For the toasted farro: Cook farro per package directions (you will need 1/2 cup cooked). Let cool. Heat 2 tsp. grapeseed oil in a large nonstick skillet over high heat. Spread farro in an even layer. Cook, stirring once, until toasted, 5 minutes.
For the red wine vinaigrette: Whisk 2 Tbsp. red wine vinegar, 1 tsp each fresh lemon juice and Dijon mustard, and 1/4 tsp. each kosher salt and black pepper. Whisk in 1/4 cup extra-virgin olive oil in a steady stream. Cover: keep at room temperature.
Arrange romaine, farro, steak, zucchini, peppers, onion, and feta in a bowl. Drizzle with vinaigrette.