Preheat the oven to 350 degrees F (175 degrees C).
Heat the oil in a large skillet over medium-high heat.
Add zucchini and onions; cook and stir until tender, about 10 minutes. Season with garlic salt, paprika, oregano and cayenne pepper, and continue cooking and stirring until fragrant.
Mix in the rice, beans and salsa and cook just until heated through.
Mix in 1 cup of Cheddar cheese until well blended.
Transfer to a 9x13 inch baking dish and top with remaining Cheddar cheese. Cover the dish with a lid or aluminum foil.
Bake for 20 minutes in the preheated oven, or until cheese is melted and bubbly.