Wieters had Tommy John surgery last June and Hardy has a strained left shoulder. Outfielder David Lough (hamstring) and infielder/outfielder Jimmy Paredes (back strain) were also put on the 15-day DL Sunday, a day before the Orioles play their opener at Tampa Bay.
Hardy, Lough and Wieters' moves are retroactive to March 27. Paredes is retroactive to April 1.
First baseman Chris Davis begins the season on the restricted list. He'll be activated Tuesday after he serves the final game of a 25-game suspension for using amphetamines without a prescription.