According to Peter Hansen as quoted by Ken Quattro at http://thecomicsdetective.blogspot.com/2010/04/return-to-wonderful-wags-of-oz.html
the early issues of this comic were direct reprints of the U.K. (and Australian) publication Wags, to which Eisner and Iger had supplied material and bought the printing plates. This is the reason for the unusual (by American standards) size of the early issues.
Format
Publication Type:
Comic Books
Color:
black and white (#1-8); color (#9 onwards)
Dimensions:
tabloid:10.5 x 14 1/2 (#1-8); 8.5 x 10.5 inches (#9); standard Golden Age U.S. (#10 onwards)