Preheat your oven to 350°F and lightly grease a 9x13-inch baking dish with olive oil. This prevents sticking and creates a beautiful golden edge on the casserole during baking.
Heat 2 tablespoons olive oil in a large skillet over medium heat, then add diced onion and cook until softened, about 3 minutes. Add minced garlic and stir constantly for 30 seconds until fragrant.
Add the uncooked rice to the skillet and toast for 2 minutes, stirring frequently to coat each grain with oil. This toasting step builds flavor depth that transforms the summer rice casserole crowd recipe into something truly special.
Stir in the chicken broth, canned tomatoes with juice, zucchini, corn, oregano, basil, salt, and pepper. Bring the mixture to a gentle boil, then immediately transfer everything to your prepared baking dish.
Cover the baking dish tightly with foil and bake for 40-45 minutes until the rice absorbs all liquid and becomes tender. Stir once halfway through cooking to ensure even distribution of vegetables throughout the rice.
Remove from oven and let rest for 5 minutes before stirring in cooked chicken pieces and half the parmesan cheese. The standing time allows the casserole to set slightly for cleaner serving.
Top with remaining parmesan and fresh parsley before serving. This garnish adds color and a fresh herb brightness that completes the dish beautifully.