Katherine Heigl exchanged vows with musician Josh Kelley in scenic Park City, Utah.

The private reception was witnessed by Grey's Anatomy costars T.R. Knight - who told PEOPLE it was "incredible and beautiful" - and Sandra Oh, as well as Private Practice star Kate Walsh and new husband Alex Young.

Taking place in a small, private tent at the Stein Eriksen Lodge, the nuptuals lasted about 30 minutes in an area decked out in white flowers and white candles. A walkway from the tent to the nearby reception was lined with white candles, illuminating the fresh snow.

The ceremony was officiated by Unitarian minister Tom Goldsmith. Heigl walked down the aisle to an acoustic song written by Kelley and performed by a cello and guitar players. According to a source, the bride and groom wrote their own vows.

[people]