The Ibrox side’s clash with Livi at the Tony Macaroni Arena was held up for several minutes after the assistant referee was struck.
The incident occurred around 15 minutes into the second half when an object was thrown from the East Stand housing the travelling Gers support.
Spence had to be treated by Lions physio Andy MacKenzie after sustaining a wound to the back of his head.
But he was able to continue and saw out the match, which Gary Holt’s side won 1-0 thanks to a Dolly Menga winner.
Gers chiefs are now set to contact Livingston’s security officers to offer assistance in tracking down the person responsible.
After the match, Rangers manager Steven Gerrard condemned the ugly scenes.
He said: “I don’t think that belongs in football does it? I think we all know that’s not right. He’s trying to do a job so that’s not right.”