Cook and stir onion, mushrooms, and bell pepper in a nonstick skillet over medium heat until just slightly tender, 5 to 10 minutes. Discard any excess water from vegetables. Transfer vegetables to a 2-quart casserole dish. Add garbanzo beans, paprika, oregano, and salt; stir to coat.
Bake in the preheated oven until vegetables are tender, about 15 minutes.