McDonald, 42, and Swenson, 38, met in 2007 when the two starred in Broadway's 110 in the Shade. They got engaged this past New Year's while on vacation in Puerto Rico.
This is the second marriage for both Broadway vets. McDonald has a daughter, Zoe Madeline, 11, from her previous marriage to bassist Peter Donovan. Swenson has two sons, Bridger, 11, and Sawyer, 8, with his first wife, actress Amy Westerby.
After four seasons on Private Practice playing Addison's BFF Dr. Naomi Bennett, McDonald left to return to the stage and recently won her record-tying fifth Tony award for her performance in Porgy and Bess. Swenson, who recently guest-starred on The Good Wife, will next appear in the new rock musical Murder Ballad.