On the penultimate Saturday of college basketball's regular season, American University and George Washington play important league games tonight while Georgetown, gearing for two big games next week, has an alleged breather.

American can gain a first-round bye in the East Coast Conference tournament by defeating Temple in an 8 o'clock tipoff at Fort Myer. Otherwise the Eagles will merely receive the home-court advantage in the opening round of the 12-team tournament. Temple is one of the East's top teams, with a 19-3 record that included a 10-point win over St. John's this week.

George Washington will close out its Eastern Eight schedule in Amherst, Mass., against the University of Massachusetts. The Colonials, now 15-7 after losing to Rutgers Wednesday, need this game to finish with a 5-5 conference record and build momentum for Wednesday's intracity showdown with Georgetown and the following week's Eastern Eight tournament at Pittsburgh.

Meanwhile, Georgetown hosts 6-18 St. Peter's at 8 o'clock in search of its 19th victory in 23 games. The 18th - ranked Hoyas had to come back from 22 points down midway in the second half to nip Manhattan, 81-80, Thursday night. And that's what worries Georgetown Coach John Thompson about St. Peter's.

"They have the kind of record that we have trouble with," he said.

In other area games, Navy hosts 10-11 Manhattan at 3:15; Drexel travels to Catholic U. for an 8 o'clock tipoff, and Baltimore U. visits George Mason at 8.

American takes a 14-10 record against Temple. The Eagles are 2-2 in ECC-East play and Temple is 3-1. An American victory will give the Eagles the first-round bye and the host role for the quarterfinals by virtue of the head-to-head victory.

The Eagles are one of the are's most inconsistent teams, mainly because of their youth. Nevertheless, only one AU team - when Kermit Washington as a senior - has won more than 16 games, which is within reach if the Eagles win tonight.

The inconsistency of the Eagles is best shown by the recent emergence of guard Stan Lamb, who played well early in the season and then tailed off before back-to-back scoring nights of 29 and 28 points in the Eagles' last two games, both victories, in which he was a combined 25 for 32 from the field.

AU's chances of beating Temple rest on its ability to grab an early lead, force the Owls out of their zone defense and then play at a pace in which Coach Jim Lynam likely would make extensive use of his "tease offense," which is the Eagles' version of the four-corners.

Lynam likely will start his "big" lineup tonight, with 6-10 Joe Mitchell replacing 6-4 forward Leon Kearney, who missed the last game with illness.

George Washington, which played poorly at Putgers, will be playing in one of the lesser-known snakepits of Eastern basketball tonight. "The Cage," as it is affectionately called, is 46 years old with stands close to the court and one of those old-time balconies. The Minutemen, a so-so team on the road, are 71-9 in The Cage since the 1970-71 season.

Massachusetts won an early-season game from the Colonials when GW blew a 16-point lead in the final 4 1/2 minutes.