Fisher, overseeing a franchise that has totaled 15 wins in the past five seasons, called for the second stringers after a 9-yard catch by Mike Hoomanawanui made it 21-0 with 6:59 to go in the half.
"I took them out because we got some production, made some plays," Fisher said. "It's a good way to finish up."
Bradford threw five touchdown passes in the preseason, all of them at home for the Rams (2-2).
"It's very satisfying," Bradford said. "The way we finished definitely shows that we're comfortable out there. I think we're moving into the regular season in a very nice way."
Harbaugh, gearing up for a Super Bowl run after losing in the AFC title game last season, started just a handful of his regulars as he does every year in the preseason finale.
"Every team does what they have to do in this game," Harbaugh said. "We didn't play a lot of our guys at all. It was a great opportunity from that perspective, to see how some of our backups match up."
Harbaugh said he hasn't decided whether to go with two or three quarterbacks, leaving Painter and Taylor, a sixth-round pick last year, on the roster bubble.
"All that's been done has been done to this point, so I'm not going to worry too much about it," said Painter, who started last year for Indianapolis after Peyton Manning was injured. "It's out of my hands, so I'll just keep rolling until they tell me not to."
Rookie Janoris Jenkins was a rare Rams starter who played into the third quarter, and made it 28-0 with a 76-yard interception return for a touchdown off a pass by Painter that deflected off Bobby Rainey's hands.
"Most definitely, I want to take it to the house," Jenkins said. "I always think that."
The Rams played well in both home games despite sparse attendance. The Edward Jones Dome, which holds 66,000, was probably about one-third full for the opening kickoff and all but empty at the end.
Fisher's plan to play his starters backfired once when first-round pick Michael Brockers injured his right ankle after getting tangled up with Jah Reid near the end of the first quarter and did not return.
Brockers was helped off the field by two trainers, but was able to put weight on the leg, then was carted off the field.
X-rays were negative and an MRI was scheduled for Friday for Brockers, who was in a walking boot but didn't think it was a serious injury.
Bradford was 11 for 16 for 175 yards and spread the ball to eight receivers, with Austin Pettis starting the scoring with a 14-yard catch capped by a dive inside the pylon.
Bradford recovered his own fumble off a center snap for a 5-yard loss the play before throwing the touchdown pass to Hoomanawanui.
Rookie kickers for both teams showed plenty of leg. The Ravens' Justin Tucker, who beat out Billy Cundiff, made a 49-yard field goal in the second half after barely missing from 57 yards near the end of the half. That was the lone miss in eight preseason attempts, including a pair from 50 yards or longer for the undrafted Tucker.
Notes: Ravens backup OLB Courtney Upshaw (shoulder) will undergo an MRI Friday. "Yeah, we're concerned," Harbaugh said. OL Justin Boren (right foot sprain) also will have an MRI, and TEs Bruce Figgins (right knee sprain) and Matt Balasavage (high left ankle sprain) were injured. ... The Rams are 3-0 against the Ravens in the preseason.
Copyright 2012 The Associated Press