Ehiogu has signed an 18-month contract with Rangers and could make his debut against Hearts on Saturday.
Parlour has been released and is reputedly training again with Arsenal, to regain full fitness. He will then look for a new club to revive his career.
Both players will have been big earners at the Riverside, so if Massimo Maccarone also follows next week Boro will make a significant reduction in the wage bill.