The striker’s goal cancelled out James Maddison’s opener which came early in the second half.
There were outings for eight of the Hatters’ ten summer signings, while Craig Mackail-Smith started, offering hope that he could be new recruit number 11.
The Scottish international spearheaded a positive opening, for a starting line-up which gave home debuts for Stephen O’Donnell, Dan Potts, Scott Cuthbert and Danny Green.
Despite a good start Luton didn’t unduly trouble City stopper Reice Charles-Cook and there was an early change when Paul Benson was forced to depart with a head injury. That gave Josh McQuoid his home bow.
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Coventry produced little in the way of attacking threat either but a Ryan Haynes long-ranger squirmed through Elliot Justham’s gloves and just over the bar.
Half time arrived without a goal but City almost broke the deadlock 35 seconds into after the restart. Justham was equal to Jim O’Brien’s shot on the turn.
Town then fell behind in the 48th minute, when the goalkeeper saved one effort but saw Maddison slam home the rebound.
The hosts did not deserved to be behind and should have drawn level soon after but had Luton’s best chance of the half, just before the break, but McQuoid couldn’t slide in Mackail-Smith’s far post cross.
Five Luton changes followed with Luke Wilkinson, Scott Griffiths, Mark O’Brien, Pelly Ruddock Mpanzu and Mark Tyler coming on – the keeper for his first appearance since Feburary.
Marriott’s introduction followed in the 76th minute and then ten minutes later the young forward collected a Ruddock Mpanzu header before slotting into the bottom corner.
Marriott almost fired another late on but Charles-Cook saved to level honours even.
Luton: Justham (Tyler, 60), O’Donnell (Wilkinson, 60), Potts (Griffiths, 60), McNulty (O’Brien, 60), Cuthbert, Lawless (Ruddock Mpanzu, 60), McGeehan (Smith, 51), Benson (McQuoid, 22), Green (Guttridge, 60) Doyle, Mackail-Smith (Marriott, 76)
Unused subs: Galliford
Attendance: 2,436 (278)