Chicken Rice Gratin – Creamy, Cheesy, Comfort-in-a-Dish

Chicken Rice Gratin is a cozy baked casserole with tender chicken, fluffy rice, a creamy garlic-onion sauce, and a blanket of melted cheese that turns golden in the oven. It’s weeknight-easy, crowd-pleasing, and perfect for using leftover rice or rotisserie chicken.

Below you’ll find the step-by-step, plus swaps (brown rice, broccoli, mushrooms), make-ahead tips, and how to keep the sauce creamy—not watery.

Why You’ll Love This Chicken Rice Gratin

Hearty + satisfying – Protein, carbs, and cheesy sauce in one pan.
Flexible – Use leftover chicken/rice and toss in your favorite veggies.
Family-friendly – Mild, creamy flavors kids love.
Great make-ahead – Assemble earlier; bake when you’re ready.

Ingredients

For the base:

3 cups cooked rice (white or brown; day-old works great)
2 cups cooked chicken, shredded or diced (rotisserie is perfect)
1 cup small broccoli florets or sliced mushrooms (optional, lightly steamed/sautéed)
1 cup shredded cheese, divided (mozzarella, Monterey Jack, or mild cheddar)

For the creamy sauce:

2 tablespoons butter
1 tablespoon olive oil (optional)
1 small onion, finely diced
2 cloves garlic, minced
3 tablespoons all-purpose flour
2 cups milk (whole or 2%) or 1½ cups milk + ½ cup chicken broth
1 teaspoon Dijon mustard (optional, for depth)
1/2 teaspoon dried thyme or Italian seasoning
1/2 teaspoon kosher salt (plus more to taste)
1/4 teaspoon black pepper
1/2 cup grated Parmesan (for the sauce)

For topping:

1/2–3/4 cup shredded cheese (the rest from above)
1/4 cup panko or breadcrumbs (optional for crunch)
1 tablespoon melted butter (if using crumbs)
Chopped parsley or chives, for garnish (optional)

How to Make Chicken Rice Gratin

1) Make the creamy sauce

Preheat oven to 375°F (190°C). Grease a 9×13-inch (or similar) baking dish.

In a saucepan, melt butter (and oil, if using) over medium heat. Sauté onion 3–4 minutes until translucent; add garlic for 30 seconds.

Sprinkle in flour and cook 1 minute, stirring. Slowly whisk in milk (and broth, if using) until smooth. Add Dijon, thyme/Italian seasoning, salt, and pepper. Simmer 3–4 minutes, whisking, until thick enough to coat a spoon. Stir in Parmesan. Taste and adjust seasoning.

2) Combine

In a large bowl, mix rice, chicken, half the shredded cheese, and the veggies (if using). Pour the hot sauce over and stir to coat evenly.

3) Assemble

Spread mixture into the baking dish. Top with remaining shredded cheese.
If using crumbs: toss panko with melted butter and sprinkle over the cheese.

4) Bake

Bake 18–25 minutes, until hot and bubbling at the edges and the top is lightly golden. For deeper color, broil 1–2 minutes at the end (watch closely).

5) Rest & serve

Let stand 5 minutes to set. Garnish with parsley/chives and serve warm.

Serving Suggestions

Simple green salad with lemon vinaigrette
Steamed green beans or roasted broccoli
Sliced tomatoes with olive oil + flaky salt
Garlic bread for extra cozy vibes

Cook’s Tips

Sauce thickness: It should be like a loose Alfredo. Too thick? Whisk in a splash of milk. Too thin? Simmer 1–2 minutes more.
Rice matters: Day-old rice stays fluffier; freshly cooked is fine—just spread on a tray 5–10 minutes to steam off excess moisture.
Cheese choice: Melty cheeses (mozzarella/Jack) give stretch; cheddar adds sharper flavor; Parmesan boosts savoriness.
Veg prep: Par-cook firm veg (broccoli, carrots) so they’re tender after baking.

Variations & Add-Ins

Mushroom + thyme: Sauté 8 oz mushrooms until golden; add to the mix.
Broccoli cheddar: Swap half the cheese for sharp cheddar; add broccoli.
Spinach artichoke: Stir in 1 cup chopped spinach + 1/2 cup chopped artichokes; add a spoon of cream cheese to the sauce.
Herby lemon: Add 1 teaspoon lemon zest and extra parsley to brighten.

Storage & Reheating

Fridge: Cover and refrigerate up to 3–4 days.
Reheat: 300°F (150°C), covered, 15–20 minutes; or microwave in short bursts with a splash of milk to keep it creamy.
Freeze: Assemble without baking, wrap tightly, and freeze up to 2 months. Thaw in the fridge, then bake as directed (add a few extra minutes).

FAQ

Can I use uncooked rice?
Use cooked rice for this method. If starting from uncooked, cook it first or use a “one-pot” baked rice method (different liquid ratios).

Can I use cream of chicken soup?
You can, but the homemade sauce tastes fresher. If using, replace the sauce with 1 can soup + milk to thin to a pourable consistency.

Gluten-free option?
Use a 1:1 gluten-free flour blend for the roux, and GF breadcrumbs (or skip crumbs).