1Preheat your oven to 375°F (190°C).
Peel and dice the potatoes into small cubes.
In a large skillet, heat the olive oil over medium heat.
Add the chopped onions and diced potatoes to the skillet. Sauté until the onions are translucent and the potatoes are slightly tender, about 10 minutes.
In a large mixing bowl, combine the cooked rice, sautéed potatoes and onions, shredded cheddar cheese, milk, salt, and black pepper. Mix well to combine.
Transfer the mixture into a greased casserole dish, spreading it evenly.
Bake in the preheated oven for 25-30 minutes, or until the top is golden and the cheese is bubbly.
Remove from the oven and let it cool for a few minutes before serving. Enjoy your Cheesy Potato Rice Casserole!