Dice the cucumber into small ¼-inch pieces. Slice the grape tomatoes in half. Dice the red onion. Roughly chop the parsley and crumble the feta.
To assemble the pitas, spread ¼ cup hummus over the surface of each pita. Top with cucumber, tomato, red onion, and a pinch of salt and pepper. Finish with a little crumbled feta, chopped parsley, and a light drizzle of olive oil.