That Championship Season. The Loeb begins the last of its summer productions tomorrow with Jason Miller's Pultizer Prize winner. Yet another play about five people trapped in a smoky room--and this one doesn't even offer a power failure, a crazed sniper, or natural disaster as its excuse. The play deals with the reunion of four former high school basketball stars and their coach. As the evening progresses, fond memories of "that championship season" drunkenly give way to confessions of failure, infidelity and corruption.

Miller's script is a catalogue of cliches about the athlete--it seems he's combined every sappy sports movie ever produced, and then thrown in some lines from "The Abe Saperstein Story" for good measure. The monologues provide some powerful moments, though, and the Loeb has rounded up a fine cast to deliver them. Wednesday, August 11 through August 21, nightly at 8 with two shows on Saturdays at 5 and 9. Tickets are $6.50 and $7.95.

Don't Bother Me, I Can't Cope. Awardwinning black musical incorporating a variety of musical and dancing styles ranging from gospel to rock, from swingtime to calypso. At the Charles Playhouse, 76 Warrenton Street, Boston. For more info call 426-6912.

The Proposition. If you still haven't seen Cambridge's long-running improvisational revue, hurry down to Inman Square to catch the Prop. Shows are Thursday at 8:30 and Friday and Saturday at 8 and 10 p.m. 241 Hampshire St., for more info call 876-0088.

The Bacchae. Euripides' classic drama, easy to follow even if you don't know Greek. The Bacchae might be summed up as the collected greatest hits of Greek drama--it's got cavorting nymphs, a blind seer, and the lecherous Dionysus to boot. Bring pillows and blankets to the Open Door Theatre, Thursdays, Fridays and Saturdays at 7 at Pinebank Park. Tickets $3; call 440-8488 for more info.