West Brom have signed Celta Vigo midfielder Okay Yokuslu and agreed a deal for Arsenal utility player Ainsley Maitland-Niles.
Turkey midfielder Yokuslu, 26, joins the Baggies on loan until the end of the season and is the club's fourth signing in this transfer window.
Maitland-Niles is expected to complete a similar move later on Monday.
Southampton and Leicester were also in contention to sign England international Maitland-Niles.
Manager Sam Allardyce thought he was going to land the 23-year-old last week, but the chance appeared to have gone when his interest became public.
However, the Gunners did not want Maitland-Niles to join a club who are in contention for a Champions League place, while Southampton felt it was taking too long to reach a deal and withdrew their interest.