Heat the oven to 350°F (177°C). Lightly grease a 5x5-inch baking dish with 1 tablespoon of olive oil.
Add the zucchini, bell pepper, onion, and broccoli to a small bowl. Toss with the remaining olive oil, Herbes de Provence, salt, and pepper, then stir in the cheese.
Transfer the vegetables to the prepared baking dish and spread them evenly.
Bake for 30 minutes, until the vegetables are tender and the cheese is melted. Serve warm.
Notes
Cut Vegetables Evenly: Slice vegetables into similar sizes so they cook at the same rate.
Consider Adding Protein: Stir in 1/4 cup of cooked lentils or chickpeas before baking for a heartier casserole.
Add Crunch: Sprinkle breadcrumbs or panko over the top before baking for a crisp finish.