The striker twice benefited from slack passing by a makeshift Saints central defence in the first half – the first after only 30 seconds when DaMarcus Beasley fed Boyd to slide the ball into the corner of the net with his left foot from 18 yards.
The Perth side gifted Rangers another goal in the 27th minute. Steven Anderson was short with a passback and Nacho Novo intercepted just before Graeme Smith got there to bring him down. Dougie McDonald pointed to the spot and Boyd fired the penalty low into the corner.
Nacho Novo netted on the rebound just after the break as Rangers closed the gap on Celtic back to two points following their rivals’ earlier win at Motherwell.