ALBION's eight-year stay in the Premier League ended with a 2-0 defeat at Crystal Palace.
The Baggies went into their final fixture of the campaign knowing relegation from the top flight was already confirmed in midweek.
And they saw their impressive five-match unbeaten run under first-team coach Darren Moore come to an end at Selhurst Park courtesy of second-half goals from Wilfried Zaha and Patrick van Aanholt.
It meant the club finished the 2018/19 campaign on 31 points at the foot of the table.
Albion, having spent 12 of the previous 16 seasons among England's elite, will now strive to replicate the immediate return from the second tier they secured in 2010.
Having kept faith with an unchanged line-up for his first five matches at the helm, including last weekend's dramatic last-gasp victory over Tottenham Hotspur, Mooro was forced into a switch as Grzegorz Krychowiak replaced the injured Matt Phillips.
Jonathan Leko was also a late call-up to the bench after substitute Sam Field sustained a minor ankle complaint in the pre-match warm-up.
The hosts dominated the early exchanges in a sunny south London, Eagles skipper Luka Milivojevic firing narrowly wide from distance before Krychowiak did likewise at the other end.
Ben Foster was called upon to save with his feet to deny Zaha after 19 minutes as Palace continued to enjoy the better of the first half.
Foster made the first save of the second period as he got down well to save from Ruben Loftus-Cheek.
Zaha placed a good opening wide of the target just before the hour mark while Andros Townsend did the same shortly after having been sent clean through.
But Zaha made no mistake in the 70th minute as he slotted home Van Aanholt's cross on the volley from six yards.
Jay Rodriguez came within inches of connecting with James McClean's low ball into the box.
But Palace doubled their advantage in the 78th minute when Van Aanholt rounded Foster and slotted home, despite the best efforts of Ahmed Hegazi on the line - ensuring Albion tasted defeat on the final day of the season.
ALBION: Foster, Nyom, Dawson, Hegazi, Gibbs, Rodriguez (Sturridge 73), Livermore, Brunt, McClean, Krychowiak (Chadli 62), Rondon (Robson-Kanu 71).
Subs: Myhill, McAuley, Leko, Burke.