Meat products are susceptible to food fraud due to their high commercial value. One possible adulteration is the undeclared substitution of high-priced meat protein by cheaper foreign proteins. A reliable detection of these added proteins is required in order to control food specification, especially regarding food fraud. A sensitive multi-method for the detection of 23 foreign protein sources (alfalfa, buckwheat, broad bean, chia, chickpea, coconut, egg, flaxseed, hemp, lentil, lupine blue, maize, milk, pea, peanut, potato, pumpkin, rapeseed, rice, sesame, sunflower, soy, and wheat) in meat products applying high performance liquid chromatography–tandem mass spectrometry (HPLC-MS/MS) has been developed. In this context, a new rapid defatting procedure, without carry-over effect, suitable for routine analysis, a robust protein extraction protocol (TRIS/HCl (1 M, pH 8.2) with 40% acetonitrile), suitable for various animal- and plant-based proteins including grain proteins, and new peptide markers for buckwheat and potato were established. A comprehensive investigation of the influence of cooking (emulsion-type sausages), grilling (hamburger patties) and maturation (salamis) showed that the detection method is robust against different types of processing. The limits of detection for all foreign protein sources were ≤ 0.02% protein and no false-positive or -negative results were obtained. •Simultaneous detection of 23 foreign protein sources in meat products.•Identification of new heat-stable peptide markers for buckwheat and potato.•Establishment of a robust extraction protocol for various foreign proteins.•Development of a new rapid defatting procedure for meat products without carry-over.•Method is suitable for differently processed meat products.