PROVIDENCE, R.I., Nov. 18--Harvard's inconsistent, often bumbling football team staggered through three miserable periods here today before regrouping for a two touchdown passing assault in the fourth quarter to out-tussle stubborn Brown, 21-6.

As 14,000 victory-starved Brown supporters cheered themselves silly for Len Jardine's revitalized athletes, Harvard's occasionally dynamic duos--halfbacks Ray Hornblower and Vic Gatto, quarterback Ric Zimmerman and end Carter Lord--finally broke loose.

Holding a sunbeam-slim 7-6 advantage with 14:55 to go in the game, Harvard took the ball on its own 20 yard line. Three line bucks got a first down, and then Zimmerman and Gatto ran twice more for 11 yards.

After Zimmerman threw an incomplete pass, Hornblower took a handoff and rolled toward the right sideline. Brown safetyman Dave Jollin charged up to contain the run, but at the last minute the sophomore Hornblower fired a bomb to Gatto deep down the sideline. The mighty Gatto caught the ball at about the Brown 25 and outran the defense to the end zone.

The Bear wasn't ready to roll over yet. On the first play from scrimmage, quarterback Hal Phillips pitched to former quarterback Mike Maznicki who stole Hornblower's thunder by flipping a 32 yard wobbler to split end Greg Kontos.

On fourth down and two at the Harvard 37, the Bruins finally ran out of chances as Crimson defensive end Bob Hoffmann bear-hugged burly fullback Steve Wormith to the ground in his own backfield.

Harvard took over and moved downfield but Tom Wynne missed his third field goal attempt of the game. Then three Brown passes went uncaught, forcing the Bruins to punt with about six minutes left.

Starting from their own 35, Hornblower and Gatto alternated carries to move the ball to the Brown 45. Then Zimmerman found the agile Lord open at the Brown 23, where Bruin Joe Petrucelli made the stop.

Gatto and Zimmerman moved the ball to the 13 where rarely-used fullback junior Ken O'Connell dove for the first down. Hornblower ground for six yards on two carries and then Zimmerman added to his Harvard career touchdown passes record by hitting Lord on a quick look-in.

It was the senior passer's 18th TD flip, breaking the mark set a decade ago by Caroll Lowenstein. Number 17 came with 55 seconds left in the first half on a fingertip grab by the spectacular pigskin Comodore Hornblower.

Until the 21 yard play, Brown had dominated, running 53 plays to Harvard's 31. The Bruins sustained two titanic drives, both of which crumpled deep in Harvard territory as the Crimson's goal line stand crew led by Captain Don Chiofaro and Joe deBettencourt, held firm.

The first time, early in the second period, a fierce pass rush induced Phillips to throw the ball away, and the second time deBettencourt collared Phillips for a two yard loss on fourth and four from the Harvard 17.

Late in the period, a 37 yard pass from Zimmerman to Lord set up the Hornblower score which sent Harvard off the field at the half with a 7-0 lead.

Brown's only score came in the opening seconds of the final period as Wormith took a Phillips pitch from the Harvard nine and bulldozed his way into paydirt. The touchdown was set up by a 57 yard Maznicki option pass to Kontos, the Bruin's outstanding end, who grabbed four throws for 128 yards on the day.