The Three Lions took an early lead in the Group H clash as Gerrard supplied the corner for Wayne Rooney to head in an opener inside six minutes.
However, the hosts posed much more of a threat after the break and duly levelled through Dejan Damjanovic on 76 minutes to ensure Montenegro remain two points clear at the top of the group.
"We stopped playing after the break for 20 or 30 minutes and, away from home, you can't afford to do that," said Gerrard.
"We stopped passing and they got a deserved equaliser. I think there was lot of experience out there and we showed that in the first half. We controlled the game. But the problem is when you are only 1-0 up you are always vulnerable.
"You've got to go on and get the second goal to get complete control and we never did that. They took control in the second half, apart from the last 10 minutes, so they deserved their draw."
Despite the stalemate, Gerrard remains convinced England can finish top of Group H by winning their remaining four fixtures.
He added: "We are still confident we can finish top of the group. We need to win all our games and we certainly need to improve on that second-half performance and play like we did [in the] first half.
"We need to put that [not having beaten Montenegro, Ukraine or Poland] right. We certainly need to get three points when we go to Ukraine and we'll need perfect results at home against Moldova, Montenegro and Poland."