The midfielder returns to the club having made 16 appearances during a loan spell in the second half of 2018-19 and will seal a transfer to the Royals on July 1, 2020.
Ejaria quickly rose through the ranks from joining the Reds in 2014 and was given his debut by Jürgen Klopp in a League Cup tie against Derby County in September 2016.
He went on to play seven more games for Liverpool that term – including two in the Premier League – before gaining experience on loan at Sunderland and then under Steven Gerrard at Rangers.