High-strength low-alloy (HSLA) steels constitute a classic metallurgical development in which alloying additions and thermomechanical processing have been brought together effectively to attain desired combinations of engineering properties through microstructural control. Moreover, the microstructural control is relatively inexpensive because the alloying elements are used only in small concentrations as carbide-formers, and the associated thermomechanical processing is introduced merely as a modification of the final hot-rolling operation. A key feature of the resulting microstructure is the small ferritic grain size that provides a favorable balance of strength and toughness in the as-rolled steel. Here, we examine the interactions in columbium-treated HSLA steels among austenite chemistry, plastic deformation, strain-induced carbonitride precipitation, recrystallization characteristics, and the subsequent transformation of the thermomechanically-processed or conditioned austenite to the final ferrite-based structures. The latter transformations are studied in order to relate the ferrite nucleation and growth as well as its ultimate morphology to the state of the prior austenite.