Miguel Reyes, 33 and Elizabeth Hernandez, 30, both of Holland Township, were transported by ambulance to a local hospital.
Wes Grady of Grand Rapids said the couple had joined his group of motorcyclists as they headed to Bike Time in Muskegon.
"We were coming up this left lane. Some cars moved over," he said.
Grady said the motorcycles started to move over as well, and the Holland couple clipped a traffic cone near the median and flipped over the handlebars.
"It sounds like he was cut off," said Sgt. Lee Adams of the Grand Haven Department of Public Safety. "He rolled the bike a couple of times."
Adams said fortunately both riders were wearing helmets.
Grady said the pair seemed disoriented and shaken up. They also had some "road rash."
The man was walking around the scene. The woman was conscious and propped up against the median wall, receiving assistance from emergency personnel.
No other information was available at the time.