David Foster and Katharine McPhee hit all the right notes during their latest date night.

The couple—who tied the knot in 2019 and share 3-year-old son Rennie—didn't miss a style beat as they stepped out for the Elton John AIDS Foundation's Oscars 2024 viewing party. (See every star here.)

For the March 10 event, held in West Hollywood, Calif., Katharine lit up the red carpet in a diamond-embellished gown that left little to the imagination with its completely sheer fabric. To add extra oomph, two black velvet bows dangled from the diamond spaghetti straps.

The Smash actress, 39, accessorized with a black jewel-shaped clutch, dainty drop earrings and nude sky-high heels. As for her glam? She opted for an old-Hollywood vibe, sweeping her hair into a deep side part and adding a voluminous wave to her bob cut. 

David, 74, let his wife steal the spotlight as he chose a classic black-and-white tuxedo for the viewing party.

This marks the pair's first Oscars party red carpet in four years after they attended the 2020 Vanity Fair Oscars event. At the time, they were about to celebrate their one-year wedding anniversary.

But now, five years into their relationship, the two have not only taken the stage and released music with one another, but they're parents to toddler Rennie.

As for what has made their marriage stronger than ever? Katharine shared the secret to their success.

"Therapy. A good therapist," Katharine exclusively told E! News in October. "Or that you just have someone in your life or another couple in your life that is helpful when there's discord, disagreements. I really feel like you can talk through most everything, but you have to have the language, the vocabulary to do that."

She added, "So that takes practice and self-awareness and having skills to facilitate those conversations."

They aren't the only couple to wow on the red carpet at Elton John's AIDS Foundation's Oscars 2024 viewing party. Keep reading to see all of the swoon-worthy fashion.

The 2024 Academy Awards air live Sunday, March 10, from 7 to 10:30 p.m. ET/4 to 7:30 p.m. PT on ABC. And don't miss E!'s Oscars red carpet starting at 2 p.m. ET/11 a.m. PT on E!.