Nottingham Forest manager Sabri Lamouchi was left to rue referee Oliver Langford's decision not to award his side a penalty as Hull condemned their hosts to consecutive Sky Bet Championship defeats with a 2-1 win at the City Ground.
Matty Cash pulled one back before Magennis saw red, but Forest were unable to force an equaliser – although they were denied what looked a stonewall penalty when Reece Burke brought down Sammy Ameobi.
"We were looking for a different result, of course," said Lamouchi. "We missed this opportunity tonight.
"We didn't create too many clear chances but maybe the big one was the clear penalty – it was clear for everyone, not for the referee.
"The referee's decision affected the game but it's not an excuse because we didn't play very quickly and we missed a lot of passes – it was our mistake."
Toral, whose last league start came in May 2018, saw his curling effort parried away by Brice Samba after 19 minutes.
Kamil Grosicki played in Bowen on the half-hour mark, but he shot straight at Samba from close range.
Lewis Grabban headed over Joe Lolley's corner from six yards, but just as Forest seemed to be finding some momentum, Hull took the lead.
Toral was at the centre of things again, playing a one-two with Callum Elder before his low shot was prodded home from close range by Magennis.
Hull started the second half on the front foot, with Grosicki picking out Bowen at the back post only for Samba to make another fine stop.
However, there was no denying Bowen his seventh goal of the season after 48 minutes when Toral squared for the 22-year-old and he coolly slotted home.
Four minutes later Forest were back in it – Cash surging forward from right-back and firing past Long.
Grabban turned a Cash cross wide from six yards moments later and Forest were denied what looked a stonewall penalty when Hull defender Burke missed a long ball over the top, Ameobi latched onto it and was then scythed down by Burke when clean through.
On that occasion referee Oliver Langford waved play on, but he had little hesitation sending Magennis off in the 67th minute for a dismal tackle on Ben Watson.
Long had to be alert to turn substitute Rafa Mir's flick from a Tiago Silva free-kick behind 10 minutes from time, and from the resulting corner Joe Worrall headed inches wide as Forest failed to convert their numerical advantage into an equaliser.
Hull boss Grant McCann was full of praise for former Arsenal youngster Toral.
"We were calm – we knew that if we could get our team selection and our plan right tonight we could cause Forest problems.
"Really pleased with Jon because he's had a frustrating time since he's been at Hull in terms of injuries. He produced a great pass for the second goal, got on the end for the first one – I'm pleased. He's a clever player."
On Magennis' moment of madness, McCann added: "Josh is frustrated – he plays on the edge anyway. He was excellent tonight so it's frustrating to lose him for three or four games.
"That's three in his last three or four games so it's not nice to lose your in-form striker."