Preheat oven to 230C Line a large roasting pan with baking paper. Place pumpkin and onion in roasting pan. Spray with oil. Season with salt and pepper. Toss well to coat. Spread vegetables over base of pan. Roast for 10 - 20 minutes or until golden. Remove from oven. Place spinach over vegetables and stand for 3 minutes or until wilted.
Grease a 3.5cm deep 16.5 x 26 cm baking dish. Line base and sides with baking paper, allowing a 2cm overhang at both long ends. Spread pumpkin, onion and spinach over base of pan. Top with feta.
Whisk eggs, milk and salt and pepper in a jug. pour over feta. Bake for 35minutes or until set. Stand for 10 minutes.