Crops with superior phosphorus (P) use efficiency (PUE) provide a financial advantage to growers and a reduced environmental burden. Progress is needed to breed winter wheat (Triticum aestivum L.) for PUE. The objectives of this thesis were to: 1) examine the P response of winter wheat genotypes across traits and environments; 2) improve methods for assessing PUE; 3) identify quantitative trait loci (QTL) for traits related to PUE; 4) assess winter wheat for root system architecture (RSA) traits important for PUE. Two-hundred winter wheat genotypes were assessed under differential P conditions over three environments. A subset with varied P response was phenotyped under controlled conditions for RSA traits, for which genetic variation was found. Genetic variation was found for P response, which was inconsistent across environments. Additionally, P treatment-specific QTL were found. Through this thesis, a PUE phenotyping method suitable for regions with historically high P inputs was developed.