The Washington Redskins are expected to sign former Atlanta Falcons veteran Steve Bartkowski as their third-string quarterback for the rest of the season, it was learned last night.

Bartkowski, 33, who was waived earlier this season after a knee injury, likely will serve as a backup to starter Jay Schroeder and reserve Babe Laufenberg.

The Redskins decided they needed a third quarterback after Schroeder cracked a rib in the victory over Philadelphia Sunday.

Schroeder practiced yesterday and is listed as probable for this Sunday's game with Cincinnati. Laufenberg will play if Schroeder cannot, Coach Joe Gibbs said.

But the Redskins, concerned about depth, began searching for an unemployed, experienced quarterback as insurance.

Bartkowski, who threw for 23,468 yards in 11 seasons with the Falcons, led the National Football League last year with a 67.3 completion percentage. He was the third-ranked quarterback in the NFC behind Joe Montana of San Francisco and Neil Lomax of St. Louis.

But he injured his right knee in Atlanta's 27-14 loss to the Redskins at RFK Stadium last November and underwent arthroscopic surgery. In all, he has had three arthroscopic and two major operations on his knee.

This season, he completed 69 of 111 passes for 738 yards and five touchdowns before reinjuring his knee, being placed on injured reserve and, finally, being waived by Atlanta.

Bartkowski, 6 feet 4 and 218 pounds, played at California before being selected by the Falcons in the first round of the draft in 1975.

To make room for Bartkowski on the roster, the Redskins likely will release rookie running back Reggie Branch, who was re-signed yesterday.