"Chris has now fully recovered from the illness that delayed the completion of his signature, and we are delighted to secure his services," Royals Director of Football Nick Hammond told the club's official website.
"He is a vastly experienced player who will offer excellent competition for both full-back positions, and greatly enhances our defensive options.
"John is a very talented footballer who can play on either wing or in a more advanced central position."
Makin was released by Leicester at the end of last season, after finishing the season on loan at Derby whilst Oster was released by Burnley, also at the end of last season.