After his next monster hit, the Cars' Heartbeat City, Lange reunited with AC/DC for 1986's Who Made Who before returning to the Def Leppard camp for 1987's Hysteria, one of the best-selling rock albums of all time. With Billy Ocean's Tear Down These Walls, Lange also moved into R&B, scoring a smash single with "Get Outta My Dreams, Get into My Car." A long layoff preceded the release of his next production, Bryan Adams' 1991 LP Waking Up the Neighbours, which generated the mega-hit "Everything I Do I Do It for You." He then hit a snag with Def Leppard's disappointing 1992 effort, Adrenalize, before returning to hitmaking form a year later with Michael Bolton's The One Thing.

By this point, Lange had already cemented his status as an in-demand producer and collaborator. His next project would bring him still greater success, however, and in some ways solidify his legacy. Lange met country artist Shania Twain soon after the release of her 1993 debut. The couple married and began working on Twain's follow-up. Released in 1995, Woman in Me was an immediate hit, spawning the inescapable radio singles "Whose Bed Have Your Boots Been Under?" and "Any Man of Mine." More importantly, it began to transform Twain's sound from polite contemporary country into straightforward pop with country overtones. The molting process was completed two years later with Come on Over. Buoyed by Lange's AOR production and pop-influenced co-writing, Twain emerged as true superstar, with only a superficial association to the country music market. Plenty of Nashville songbirds followed the Lange/Twain team's lead, kicking the mud off their high heels to embrace the mainstream with gusto.

In 1999, Lange moved back into pop by producing some of the tracks on the Backstreet Boys' hit album Millennium; that same year, he also helmed Celine Dion's All the Way: A Decade of Song. Contributions to the international version of Britney Spears' Oops!...I Did It Again followed. Lange's magic touch struck again in 2001, when he produced the entirety of the Corrs' In Blue and co-wrote "Breathless," the album's effortlessly sugary hit single. In November 2002, he and his wife reunited for Up! The album was initially released in three versions, with each one tweaked alternately for pop, country, and international audiences. The move was derided by some, but it only proved Lange's prowess as a pop producer without need for genre qualification. Unfortunately, the couple's chemistry in the studio had all but fizzled out at home, leading to a split in 2008 and a divorce shortly thereafter. Meanwhile, Lange continued working in sporadic spurts, producing Nickelback's multi-platinum 2008 effort Dark Horse and Maroon 5's Hands All Over.