Struve, who takes a three-fight win streak into the UFC on Fuel TV main event, weighed 251 pounds. The undefeated Miocic tipped the scale at 239 pounds.
Miocic has a professional record of 9-0; he's 3-0 in UFC. Struve, who stands 6-foot-11½ and is 24-5 professionally, represents the most-skilled mixed martial artist Miocic has ever faced.
Hardy (24-10, with one no-contest) ended a four-bout skid with a first-round knockout of Duane Ludwig in May.
In his most recent outing, on May 15, Sadollah (6-3) defeated Jorge Lopez by split decision.
Every other fighter on the card made weight.
Welterweight DaMarques Johnson came in at 183, eight pounds over the limit, but will not be penalized, as he accepted the fight on one week's notice.
Johnson faces Gunnar Nelson (175 pounds) in an agreed-upon catch-weight bout.