Pulitzer- and Tony-winning Broadway play “August: Osage County” will shutter June 28, following several months of dwindling box office.

Producers were hoping sales would pick up with the May 26 addition of Phylicia Rashad to the cast, but grosses did not improve significantly. Last week “August” grossed about $225,000 and played to auds that averaged around 60% of capacity.

Still, “August,” which began perfs in October 2007, eked out a relatively lengthy run for a non-musical. The 20-month stint surpassed the runs of previous hit plays including “Doubt” and “Master Class” — although not “Proof,” which ran for more than two years, or “The Tale of the Allergist’s Wife,” which came in at just under two.

The Broadway audience for plays is generally considered much smaller than the aud for musicals, with razzle-dazzle tuner fare proving a far broader draw for tourist biz. Plus, with the proliferation of star-driven limited runs, even hit non-tuners often shutter after limited engagements of less than six months.

Tracy Letts’ three-hour-plus family drama “August,” which originated at Chicago’s Steppenwolf Theater in a lauded run, had a rocky start on the Rialto. Soon after it began previews in Gotham, the play was forced to go dark due to the stagehands strike in November 2007.

But rave reviews helped propel business for the show, which recouped its $2.5 million capitalization costs in about six months. “August” went on to win five Tonys, including play, and pick up the Pulitzer.

In recent weeks, though, sales began to peter out, sometimes dipping below the $200,000-per-week mark.

Current cast of “August” includes Rashad, Elizabeth Ashley, John Cullum and Frank Wood.

A national tour of the show will launch in Denver in July, with Estelle Parsons reprising the matriarch role she played on Broadway (where she replaced Deanna Dunagan, who scored the Tony for her perf).

“August” was produced on the Rialto by Jeffrey Richards, Jean Doumanian, Steve Traxler and Jerry Frankel, among others. Those producers will serve as leads for a Broadway production this fall of Letts’ play “Superior Donuts.”