Preheat your oven to 350°F (175°C). Grease your baking dish with olive oil.

In a skillet, heat olive oil over medium heat. Sauté onion for 4-5 minutes until translucent. Add garlic and sauté for an additional minute.

Wash and chop fresh spinach; if using frozen, thaw and drain well. Combine spinach with the sautéed onion and garlic.

In a large bowl, whisk eggs, milk, and feta cheese together. Fold in the spinach mixture until well combined.

Pour mixture into the greased baking dish and sprinkle bread crumbs on top.

Bake for 30-35 minutes until the center is set and the top is golden brown.

Allow to cool for 5-10 minutes, then cut into squares and serve warm.