Preheat the oven to 350°F. Spray a 1-quart baking dish with non-stick baking spray; set aside.

Into a medium skillet over medium-high heat, add the olive oil. When the oil is hot, add onions and cook for 2 minutes, stirring frequently until softened. Add the garlic and continue cooking for an additional 30 seconds. Remove from heat and transfer to a medium-sized mixing bowl.

Add the cream cheese, mozzarella, parmesan, salt, and pepper. Stir to combine and adjust seasoning to taste. Stir in the chopped broccoli.

Transfer the mixture to the prepared baking dish. Bake for 25 minutes, until the dip is heated through and the edges are lightly golden. Serve hot.