The mobility of individual adatoms and of different structural elements in the O/Cu system is analyzed on the basis of scanning tunneling microscopy data. A value of D≊10−14 cm2 s−1 for the coefficient of self‐diffusion at 300 K on the bare Cu(110) surface is derived from the motion of steps. Supply of Cu adatoms by ‘‘evaporation’’ from steps rather than the migration of individual O or Cu adatoms on the terraces is rate limiting for the ‘‘added row’’ reconstruction processes, leading to a slowdown of the transformation with increasing conversion. The kinetics for the (1×1)→(2×1) reconstruction is shown to follow that behavior, supporting a supply‐controlled rather than a growth‐controlled mechanism for (2×1) formation. The role of lateral interactions between neighboring ‐Cu–O–Cu‐ strings and of lateral displacements of entire such strings for the stabilization and growth of (2×1) islands and for the removal of antiphase domain boundaries (Ostwald ripening) are discussed. Conversion into the higher coverage c(6×2)O phase, again associated with a change in topmost layer Cu density and thus with mass transport, occurs in the direct vicinity of the location of the activated process, contrary to (2×1)O formation, and can be described as a local solid‐solid transformation.