Heat oven to 400°F / 200°C. Grease a 9 × 13-inch dish.
Whisk eggs, milk, flour, salt, pepper and herb de Provence, add spinach, chopped peppers and about the crumbled feta.
Pour the batter in the lined dish.
Bake 40 minutes, until puffed, golden and just set in the center.
Rest 10 minutes before serving.
