Grant is a 27-year-old global financier from England. Lamas, the daughter of former TV star Lorenzo Lamas, is a 22-year-old actress from Los Angeles.
"My knees gave out and I started shaking," Lamas told People magazine after the proposal. "It was a fairytale proposal like I've always dreamed about. I forgot that there (were) cameras around. In that moment, it was just Matt and I, and it was the most amazing moment of my entire life."
Grant called the moment "incredible."
"It (was) a beautiful setting, a beautiful day. Shayne (looked) absolutely exquisite," he told People.
Lamas said she wants to marry Grant, but not until she is ready.
"There's still a lot of growing to do in our relationship. We will not tie the knot until I am mentally and physically prepared as well as Matt," she said.
The couple couldn't be seen in public for the past few months while the show aired, in an effort to keep under wraps the name of the woman with whom Grant would choose to have a relationship.
Aaron Carter is still in love with Hilary Duff
NBC reportedly holds celebs hostage to Jimmy Fallon's show