Saracens won a second successive Premier 15s title after seeing off a late comeback from Harlequins.
England forward Poppy Cleall and fly-half Zoe Harrison both crossed twice for the defending champions.
Saracens wing Sydney Gregson also scored in a dominant first half which saw Quins rarely venture into the opposition's 22.
But Harlequins improved after the break and were rewarded with tries from Vickii Cornborough and Rachael Burford.
Quins full-back Emily Scott scored a penalty, but Harrison replied with two of her own to ensure victory for Sarries.
The match was a repeat of last season's final, when Saracens were crowned champions of the inaugural Premier 15s - the top tier of English women's rugby.
Saracens were without injured England forwards Bryony Cleall, Vicky Fleetwood and Marlie Packer but they still dominated the first half.
It was a fast start as number eight Poppy Cleall - twin sister of Bryony - went over from a driving maul off a line-out after a perfectly placed kick to the corner by Harrison.
The defending champions threatened again almost immediately and it was not long before Gregson went over in the right corner after fast hands from Cleall and England prop Hannah Botterman.
Harrison then confounded the Harlequins defence with a show and go to score Saracens' third, before player-of-the-match Cleall claimed her second try off another line-out.
Harlequins rarely ventured into Saracens' 22 in the first half, committing repeated handling errors and being smothered by Sarries' defence.
A yellow card for Jodie Rettie after the Saracens flanker was offside just before half-time gave Quins an advantage.
But Sarries even came out on top in this period when Harrison crossed again after more impressive footwork.
Quins come back
It was an improved Harlequins performance after the break, but the south-west Londoners still struggled to break through the impenetrable Saracens wall.
Hannah Botterman's ferocious work at the breakdown stopped several Quins attacks but they eventually drove over and Cornborough touched down.
Harlequins soon built momentum again and England centre Burford capitalised as she burrowed over from close range.
Trouble from the tee
The only blot on Saracens' brilliant performance was Harrison's kicking, after the fly-half made three kicks from eight in total.
There has been some talk this season about how the women's game has room for improvement in this area, and the blustery conditions did not make life any easier for Harrison.
Given that women often start rugby later in life, they do not get as much time to develop their kicking skills and this was demonstrated in the fly-half's mixed results from the tee - although her kicks from hand were more impressive.
The crowd of 2,590 at Franklin's Gardens was perhaps also disappointing after 4,837 attended a Quins game at The Stoop in the regular season.
We embraced the pressure - what they said
Saracens head coach Alex Austerberry: "I'm ecstatic. It's a combination of a lot of people's hard work.
"People build pressure on you from the outside. We've worked hard and the players have shown great character throughout. We embraced the pressure and got on pretty well.
"Plans are afoot already for next season which is important because the league is going to get better and better.
"The group want to be the best that they can be and if we keep with that mentality that will drive standards."
Harlequins co-head coach Gary Street: "I was frustrated with the first half, I don't think we've played like that ever.
"But we've got to look forward. It's our second year as Harlequins with a young squad and we know we'll be stronger next year.
"At half-time I told them to be themselves and play how we know we can play, but 27-0 is too big to come back to.
"It was surprising as much as it was disappointing."
Saracens: McKenna; Gregson, Casey, Cattell, Clapp (c); Harrison, Gulliver; Perry, Campbell, Botterman; Green, Galligan, Rettie, Newman, Cleall.
Replacements: Duffy, Layola, Searcy, Bebbington, Swords, Vistisen, Miell.
Harlequins: Scott, Cowell, Camara, Burford (c), Breach; Green, Riley; Cornborough Catlin, Edwards, Scott, McCormack, Fletcher, Butler, Konkel.
Replacements: Lyons, Viksten, Voyle, Saynor, Packer, Myers, Wilcock.