Quintanilla attended the University of Colorado Boulder, where in 1993 he received a Bachelor of Arts degree in political science. From 1991 to 1993, he was a reporter and columnist for the Daily Camera in Boulder. He spent a summer as an editorial assistant for NPR in Washington D.C.

From 1994 to 1999, Quintanilla served as a staff reporter for The Wall Street Journal where he wrote full-time for the newspaper’s Chicago bureau, covering airlines, manufacturing and economic issues. He also wrote a weekly column on workplace issues and on-the-job trends for the newspaper’s front page.

From 1999 to 2002, he served as correspondent for several CNBC programs including Business Center as well as a special correspondent for Fox X-press on Fox News. Prior to joining NBC, Quintanilla served as co-anchor for CNBC’s early-morning program, Wake Up Call.

Quintanilla won an Emmy Award, an Edward R. Murrow Award and a Peabody Award for his coverage of Hurricane Katrina in 2005.

In 2007, he traveled to China to cover McDonald’s efforts in the country for CNBC’s documentary Big Mac: Inside the McDonald’s Empire.

From 2010 until September 2015, Quintanilla substitute-anchored weekday and weekend editions of NBC Nightly News, covering when hosts Brian Williams and Lester Holt were on assignment or away. He also substitute co-hosted Today.

In July 2011, Quintanilla left Squawk Box to join Squawk on the Street.

In June 2014, Quintanilla joined HBO Real Sports as a correspondent. He presented a story on Stephon Marbury in January 2015.

On October 28, 2015, Quintanilla was one of CNBC’s moderators of the third of the 2016 Republican Party presidential debates and forums at the University of Colorado Boulder. He and his CNBC co-moderators were heavily criticized for being ill-prepared and rude to the candidates.

Quintanilla is married to Judy Chung, a former TV producer who now works as a product manager for Ralph Lauren. In 2017, they purchased a new house in Bridgehampton, New York for $3.2 million.