Heat the oil in a large skillet or sauté pan over medium-high heat. Brown the ground beef without disturbing it for 4 minutes. Break the beef up and add the onion. Continue cooking, stirring, for 3 to 4 minutes, until the beef is no longer pink and the onions are translucent.
Add the rice, chili powder, salt, pepper, tomato sauce, and water; bring to a boil. Reduce the heat to low, cover, and simmer for 15 to 20 minutes or until the rice is tender.