"I really enjoyed my time here on loan earlier this season and when the club showed an interest in offering me a permanent deal, I was made up," he said.
"It's a great time to be at QPR. Big things are going to happen here, the new owners are very ambitious."
Ephraim made just one senior appearance for the Hammers and spent much of last season out on loan at Colchester United.
Connolly, 20, has also signed a three-year deal with the Rs. The pair follow hot on the heels of fellow newboys Kieran Lee and Gavin Mahon.
"Arsenal provided me with a great launch-pad, but I need to be playing first-team football at my age and this is a fantastic club for me to pursue my career at," he said.
"I know what the Championship is all about after my spell at Colchester United."
Connolly spent the first half of the current campaign on loan at Colchester United, while last term he spent nearly two months with Bournemouth.
Rangers are also expected to sign striker Patrick Agyemang from Championship strugglers Preston.