The Eagles traded up from the 15th spot in the first round to the 12th slot to select Cox, who was regarded as the top-rated defensive tackle in the draft by NFLDraftScout.com.
The 6-4, 294-pound Mississippi State product ran a 4.79-second 40-yard dash and a 1.63 10-yard split at the combine in February, unheard of for someone his size.
He gives Eagles defensive line coach Jim Washburn a player with the versatility and athleticism to play both inside or outside in the team's varied personnel packages.
"When God made him, he made him to be in this system right here," Washburn said, referring to the wide-nine his front four plays. "He's a good one and I'm excited about him. I'm not going to coach forever, and if this is my last big-time project here, this would be fun."