Edgar (15-4-1) will fight for the second time at 145 pounds. He was on the short end of a unanimous decision during his Feb. 2 featherweight debut against titleholder Jose Aldo.
Edgar has dropped three fights in a row. He lost the 155-pound title to Benson Henderson in February 2012, then suffered a split-decision setback during their title rematch in August 2012.
Oliveira (16-3 with one no-contest) hopes to rebound from a first-round knockout to Swanson at UFC 152 in September. The bout was contested slightly above 146 pounds after Oliveira failed to make the mandatory featherweight nontitle limit. Oliveira is 2-1 since leaving the lightweight ranks in 2011 to compete at featherweight.
After losing his featherweight debut, Edgar expressed interest in facing Swanson, who is currently riding a four-fight win streak. Swanson (19-5) put himself in the title picture with a unanimous decision over Dustin Poirier on Feb. 16.
Siver was originally slated to meet Swanson on Feb. 16, but an injury forced him to withdraw. The former lightweight will make his third appearance at 145, where he is currently unbeaten.
Edgar, Swanson and Siver are ranked second, seventh and eighth, respectively, among featherweights by ESPN.com.