Preheat oven to 160 °C. Line a 6 cm-deep x 22 cm x 32 cm rectangular baking dish with baking paper and spray with olive oil.
Heat olive oil in a large, deep frying pan over medium heat.
Stir-fry onion and garlic for 4-5 minutes or until softened.
Add capsicum and zucchini, cook, stirring for 2 minutes. Add the kale and cook, stirring for 1-2 minutes, or until wilted. Set aside to cool.
Whisk eggs, milk and parsley in a large bowl.
Scatter the vegetables in the baking tray, and then pour egg mixture over the vegetables. Sprinkle the crumbled fetta evenly.
Bake for 30-35 minutes or until golden and set. Cut into 5 slices.