He is best known for his roles as Victor Joseph in Smoke Signals; Frank Fencepost in Dance Me Outside; Tommy on Walker, Texas Ranger; Kickin' Wing in Joe Dirt; U.S. Marine Corporal Ira Hayes in Flags of Our Fathers; Private Ben Yahzee in Windtalkers; Dr. Charles Eastman (Ohiyesa) in Bury My Heart at Wounded Knee; NYPD Detective Chester Lake in Law & Order: Special Victims Unit; and Officer Jim Chee in the film adaptations of Skinwalkers, Coyote Waits and A Thief of Time.

Most recently he has starred in Hostiles (2017) as Black Hawk and the Netflix original film Juanita (2019) as Jess Gardiner and Edward Nappo in Jane Campion's The Power of the Dog.

[5] At age 18, Beach won a small role in the miniseries Lost in the Barrens, based on the Farley Mowat novel.

In the following years, he continued to work in local theatre and guest-starred on television shows such as Walker, Texas Ranger and Touched by an Angel.

After his performance in Dance Me Outside, he starred in Smoke Signals, which was nominated for the Grand Jury Prize at the Sundance Film Festival.

Beach appeared in Helen Lee's The Art of Woo and the 2001 hit Joe Dirt as Kickin' Wing, a Native American fireworks salesman.

The producers of Joe Dirt had originally wanted to hire Evan Adams for the parody of his character in Smoke Signals, but accidentally called Beach instead.

[6] In 2002, Windtalkers, starring Beach, was released in theatres; it was about Navajo codetalkers working with the US Marines during World War II.

He used this language in his next project, Skinwalkers, based on a novel by Tony Hillerman and directed by Chris Eyre, who had given him his breakout role in Smoke Signals.

[8] In 2007, Beach starred in HBO Films' adaptation of Dee Brown's history, Bury My Heart at Wounded Knee.

[10][11] He later stated he grew disillusioned with the strictly procedural nature of the show and opted to leave after the finish of the ninth season.

On February 10, 2010, it was announced that Beach will portray Tommy Prince, the Canadian war hero, in an upcoming movie about his life.