The couple met back in 2012 and began dating three years later.
According to the outlet, Schmidt popped the question on Wednesday at Radio City Music Hall with band members Logan Henderson, Carlos PenaVega and James Maslow all in attendance.
The location is a special one for the couple, as it's the place they first met a decade ago at one of Big Time Rush's shows, People reports. The pair started dating three years later, in March 2015, according to the outlet.
Schmidt shared a pic of himself down on one knee on Instagram, revealing the moment he asked Turkovich to be his wife.
"My heart and soul," he captioned the romantic shot. "I’ll love you forever."
One day after Schmidt got engaged, Big Time Rush released their latest single, "Honey." The band is set to perform a sold-out show at Madison Square Garden Thursday night as part of their Forever Tour.