Wieters had Tommy John surgery in 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 on Sunday, a day before the Orioles play their opener at Tampa Bay.
The 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 will be activated Tuesday after he serves the final game of a 25-game suspension for using amphetamines without a prescription.