Quins ran out 23-6 victors to go top of Pool One in the LV= Cup but the scoreline flattered the hosts in a scrappy match which saw both sides guilty of regularly turning over possession.
Kingston said: "Some of our boys were a little bit rusty as they haven't played a lot of meaningful rugby in recent weeks. The pitch was very tacky and with snow on it all week it had become heavy and difficult to play on."
Quins led only 10-6 at half-time thanks to Mark Lambert's converted try with battling London Welsh replying courtesy of two penalties from Alex Davies.
The home side then eased away after the interval with Ben Botica adding two more penalties to go with his first-half effort before then converting Dave Ward's 74th-minute try.
Although they failed to get on the scoresheet in the second half, the 17-point gap at the final whistle was tough on a London Welsh side who fought hard.
Coach Lyn Jones said: "We are disappointed because we deserved more.
"It was a competitive match and we knew we had to be physical to stop them. They are a hugely skilled side and had a bit more speed than us."
London Welsh are still pointless after losing their first three games in the LV= Cup but Jones points out the competition is not at the top of their priorities at present.
"We got promoted and were entered for three competitions, only one - the Premiership - is important to us at this stage," he said. "Maybe in two or three season's time we can be more competitive in the LV and Amlin but at the moment it gives us an opportunity to rest our players."
- Sports & Recreation
- London Welsh