Combine all dressing ingredients in a small bowl and whisk to combine until smooth. Store in the fridge until ready to use.
Preheat your grill to high heat (about 450℉).
Pat the steak dry with paper towels and sprinkle both sides generously with salt and pepper.
Thread cherry tomatoes and quartered onions onto skewers. Brush them lightly with oil and sprinkle with salt and pepper.
Once your grill is hot, place both the flank steak and veggie skewers on it. Grill veggies for about 5-8 minutes, turning occasionally until softened and slightly charred.
Grill the flank steak for about 4–5 minutes per side for medium-rare.
Remove your steak from the grill onto a plate; cover loosely and let it rest for about ten minutes before slicing thinly against the grain.
Divide chopped romaine between four plates or shallow bowls. Top each bowl with sliced steak, grilled vegetables, dollops of hummus, chopped cucumbers, olives, and crumbled feta cheese.
Drizzle each bowl with Herbed-Yogurt Dressing and add lemon wedges or torn fresh mint leaves if desired.