The Eagles team that included three of the Connacht side that had a bonus point victory at Enisei-STM in the Challenge Cup the week previous, produced a battle-hardened display in Castle Park. Doncaster went 7-0 up after six minutes when a Eagles handling error was punished by full-back Paul Jarvis, and Dougie Flockhart tapped over the conversion.
The Eagles were still in the game, but Rory Moloney was yellow-carded, and Tyson Lewis crossed for Knights' second try.
Glen Young drove home their advantage after the break, and Jarvis sealed the bonus point on the hour.
A late try from replacement back row Stephen McVeigh was well taken after a powerful break from fullback Ciaran Gaffney but it will serve as little consolation to Nigel Carolan's men who will want to return to the form shown in the interpro games when they travel to play Jersey RFC in mid December.
DONCASTER KNIGHTS - P Jarvis; D Flockhart, A Bulumakau, W Hurrell, T Lewis; D Cusack, M Heaney; R List, B Hunter, WG John; T Hotson, G Young; L Makaafi, M Hills, A Shaw.
CONNACHT EAGLES - C Gaffney; A Leavy, C Brennan, D McSharry, E O'Keeffe; C McKeon, C Blade; J Walshe, P O'Toole, S Meunargia; P Claffey, C Gallagher; J Connolly, R Moloney, S O'Brien (captain)