The alternating copolymerization of cis-cydooctene and 1-substituted oxanorbornenes with commercially available ruthenium based olefin metathesis catalysts was investigated We determined that RuCl2(CHPh)(PCy3)2 performs a standard alternating copolymerization with these monomers. Unexpectedly, another route to the desired alternating copolymer was revealed The "sequence editing" route involves the initial polymerization of cis-cyclooctene, followed a ring-opening cross metathesis step that introduces the 1-substituted oxanorbornene monomer in the polycyclooctene chain and largely avoids oxanorborene homopolymerization. Selectivity for alternating diads in the polymer exceeds 90%. Polymer molecular weight can be controlled by linear olefin chain transfer reagents during sequence editing.