All three featured as Quins went down 37-8 to the French giants at the Stade Mayol, with former England fly-half Jonny Wilkinson kicking 17 points.
England head coach Stuart Lancaster signalled his intention to blood young talent during the RBS 6 Nations, where a new-look Red Rose outfit won four times.
And O'Shea is convinced that, despite the disappointment of the result, facing such top quality opponents will stand his youngsters in good stead in the long term.
"We just came up against a very good side," the Quins boss admitted after the match.
"Toulon don't lose here very often and they were very much at full strength.
"And I've got to credit some of our younger guys for keeping going until the bitter end.
"We had people like Will Collier at just 21 coming on at tight-head, Rob Buchanan at 20 had 50 minutes at hooker in that sort of atmosphere against Sebastien Bruno, and it was also part of Rory Clegg's continued development."
Quins have high hopes for Clegg at fly-half, Collier at prop and Buchanan at hooker, and all three are rated potential England players of the future as Lancaster looks to build towards the 2015 World Cup.
The trio have already represented the Red Rose at major international tournaments at Under-16, Under-18 and Under-20 level.
Collier and Buchanan also formed part of the Under-20 side which reached the final of last summer's Junior World Cup in Italy, ultimately losing 22-33 to New Zealand.
"We spoke about getting an early score ourselves because that's what you need when you come to places like this but we gave penalties away when we had possession," added O'Shea.
"We had two lineouts to try and build our own momentum but we coughed them up and we lost the battle around the contact area against a very physical team."