Cut chicken into 1.5cm-thick strips. Combine with half the zest and lemon juice, garlic and 1 tbs oil. Season and mix well. Set aside to marinate.
Place couscous in a large heatproof bowl. Add beetroot and stir in 1 cup boiling water. Cover and stand for 5 minutes, then fluff grains with a fork. Toss through remaining lemon juice. Season well. Set aside.
Thread chicken onto 12 skewers. Heat a large grill pan or barbecue plate over high heat. Cook skewers for 3-4 minutes on each side or until golden brown and cooked through.
Serve skewers with couscous, cucumber and feta, drizzled with remaining oil. Top with dill, remaining zest and lemon wedges.