Strikers Byron Alvarez and Fadi Afash combined for the two Portland goals, with Afash tallying the game-winner.
The Timbers (18-7-3, 57pts) wrap up their most successful A-League regular season to date as the team with the best record in the league, surpassing Montreal on the final day of competition.
The ten-game unbeaten streak is a franchise high for the Timbers, who have allowed just six goals during the run while topping the A-League with 58 strikes on the season.
Portland will square off with archrival Seattle in the Western Conference Semifinals beginning on Wednesday, Sept. 1 at PGE Park. The second leg of the two-game aggregate goal series will move to Seattle on Sunday, Sept. 5.
The game-winning goal came in the 77th minute when Afash put on a clinic inside the box, back-heeling the ball past several unsuspecting defenders and Milwaukee goalkeeper Jeff Richey.
In the 49th minute, Jake Sagare dished left to Alvarez, who rang up his 16th goal of the season from close range for the 1-0 lead.
Moments after Milwaukee’s Nino Marcantonio was tossed from the match with a red card, Todd Dusosky looped a free kick from Johnny Torres over the head of Portland goalkeeper Josh Saunders, making it a 1-1 match.
In first-half action, Sagare got loose in the 22nd, squeezing off a shot from the left side that was challenged and put out of play by the Milwaukee ‘keeper.
The Wave United’s Ibrahim Kante registered two shots in the first half, most notably a 40-yard laser that missed high and to the left.
Greg Howes nearly equalized in stoppage time of the second half for Milwaukee (12-12-4, 40pts), but Saunders came away with the clean save, his fourth of the evening, to preserve the victory.
Wednesday’s conference semifinal playoff match against Seattle will kick off at 7 p.m. (Pacific) at PGE Park.
TIMBERS NOTES: Playoff tickets are available for purchase at the PGE Park box office and at various Ticketmaster outlets in the Portland area. Group tickets are available by calling (503) 553-5555.
SCORING SUMMARY: Alvarez, 49’ (Sagare); Todd Dusosky, 68’ (Torres); Afash, 77’ (Thompson).
PENALTY SUMMARY: MIL Morman, YC (45’), Torres, YC (45’), Marcantonio, RC (66’); POR Gordon, YC (38’).
LINEUPS: MILWAUKEE (12-12-4) Richey GK, Lawrence D, Dombrowski D, Morman D (Marcantonio 45’), Hammes D, Schmidt M, Torres M, Beasley M (Burk 78’), Walls M (Fontana 45’), Kante F (Howes 45’), Takawira F (Todd Dusosky 45’); PORTLAND (18-7-3) J. Saunders GK, Morrison D, Wilkinson D, Thompson D, Alcaraz-Cuellar M, Winters M, Benedetti M (Bengard 8’), Miranda M, Miranda M, Alvarez F (Afash 73’), Gordon F (Antoniuk 45’).