For Beck to leap into the air while his momentum is carrying him swiftly eastward, and throw across his body and against its momentum, and make the pass travel as far west by northwest across the field as it did, was miraculous. McMahon's throw to Brown wasn't difficult, nor was it difficult to track Brown running downfield into a crowd. Brown's catch was spectacular, truly, but so was Mitch Mathews' catch against Nebraska, and Glen Koslowski's against Michigan. The determination of "most miraculous" seems to turn on which player you're focusing on. As someone who's been watching BYU football since 1960, I can at least say that Beck's throw to Harline was the most miraculous and spectacular QB play I've ever seen a BYU QB make.
Also, for Beck to even see Harline while he's sprinting east and Harline is sliding west through heavy and chaotic traffic in the end zone, was a miracle all its own.