This study on raw ground beef patties evaluated: resistance of STEC strains inoculated at 6 log CFU/g (O157:H7, O26, O45, O103, O111, O121, and O145) subjected to 350, 450 and 600 MPa, for 5 min at 10 °C; effectiveness of pressure for initial loads (2, 3 and 4 log CFU/g) of O157:H7; and general impact of high hydrostatic pressure (HHP) on raw patties. For 600 MPa treatments and 6 log CFU/g load of STEC, ~5 log CFU/g reductions were obtained with all strains. For 450 MPa, differences in baroresistance among strains became evident. When inoculating O157:H7 at different loads, counts after 600 MPa fell below quantification limits, though virulence genes were detected for the two highest loads. Additionally, HHP reduced native aerobic microbiota to <1 log CFU/g and slightly affected a* and b* color values. Montecarlo simulation was used to estimate potential initial counts of STEC that allow compliance with existing regulatory limits after applying HHP, showing that absence of STEC studied can be achieved in 65 g of patties provided initial loads are ~2 log CFU/g. Finally, HHP treatments at 600 MPa and mild temperatures can be considered a valid non-thermal processing technology to achieve 5 log CFU/g reductions.