The oncogenic ability of the epidermal growth factor receptor (EGFR) is mediated by increasing its signaling capacity, thus promoting cellular proliferation, migratory potential and evasion of apoptosis. As such, the EGFR signaling pathway has been the focus of many studies aimed at deciphering the network topology facilitating this plethora of phenotypic outcomes. Although the EGFR has the potential to activate several signaling cascades, the specific timing and extent of activation determines specificity. Here, we investigate signal specificity by comparing two different signals, which result in different cellular behaviors. This approach offers the ability to address lateral signaling modalities as well as classical horizontal signaling. We have recently characterized a two-input system, wherein immortalized mammary epithelial (MCF10A) cells respond stereotypically to two different signals: EGF causes cell migration while serum promotes cell proliferation. In this study, our aim is to decipher the key post-translational modifications (PTM) following these two stimuli. We use the Stable Isotope Labeling with Amino acids in Cell culture (SILAC) method coupled to tandem mass spectrometry (LC/MS/MS) to identify in an unbiased and global manner the dynamics of the PTMs that are elicited by EGF or serum treatments along several time points in the MCF10A cells. Our data analysis reveals, as expected, that most of the phosphorylation events occur on serine residues, a minority on threonine and a handful are tyrosine phosphorylation sites. Quantitatively, rapid and transient phosphorylation patterns are observed both in terms of induction as well as reduction. Serum stimulation leads to overall more phosphorylation events compared to EGF, as can be expected by addition of an array of factors when compared to a single agent. Altogether, we have produced a large dataset of highly specific phosphorylation events that emanate from distinct stimuli, and lead to defined phenotypes. Further analysis will identify key proteins that are modified and regulate these processes.