First, heat olive oil in a skillet over medium heat. Add the minced garlic and cook until fragrant. Then, toss in the chopped spinach, salt, pepper, and oregano, cooking until the spinach is wilted.
Slice the French bread lengthwise, but not all the way through—leave a hinge. Hollow out some of the soft bread from the center to make room for the filling.
Mix the feta and mozzarella cheese into the cooked spinach. Spread the mixture evenly inside the hollowed-out bread. Make sure every bite gets a cheesy, spinachy taste.
Preheat your oven to 375°F (190°C). Place the stuffed bread on a baking sheet and bake for 15–20 minutes, until the cheese is melted and the crust is golden.
Remove from the oven and let it rest for a few minutes. Slice into portions and serve warm for the best flavor.