Genomic surveillance of antimicrobial resistance (AMR) in healthy animals ensures catching early trends in antimicrobial resistance gene (ARG) status, protects the food chain and safeguards antibiotic usage. As part of the Pathogen Surveillance in Agriculture, Food and Environment (PATH-SAFE) programme, we aimed to evaluate ARGs in Escherichia coli isolated from caecal content samples from healthy beef cattle (n=361). Sampling took place at slaughter across Great Britain for 8 months (2023/2024). Ninety-seven presumptive extended spectrum beta-lactamase (ESBL/AmpC) producing- E. coli were cultivated in ESBL selective media and classified phenotypically by Minimum Inhibitory Concentration. Whole genomes were generated and evaluated for ARGs using AMRFinderPlus (v.4.0.3). All strains phenotypically classified as ESBL (n=67) harboured a blaCTX-M gene, with 79.1% (53/67) of these being blaCTX-M-15. In one third (69.2%; 18/26) of phenotypically AmpC strains (26.8%; 26/97), point mutation C-42T in AmpC promoter gene were detected. blaCMY-2 (19.2%; 5/26) and blaDHA-1 (3.8%; 1/26) were also described. Of the AmpC encoding strains, 11.5% (3/26) also contain blaTEM, TEM-35 and CTX-M-15 genes, despite not being detected by phenotyping. Four strains were classified as ESBL and AmpC but genotypically, two harboured only blaCTX-M-15 and two harboured blaDHA-1 and C-42T in promoter AmpC gene. Among all strains sequenced, 46.3% (45/97) were multidrug resistant, with ARGs against quinolones (65), tetracycline (36) and aminoglycosides (31) more frequently found. Resistance against biocide agents was identified in 12.3% (12/97). Genomic analysis enhances the depth of research and surveillance and understanding the AMR landscape.