The ability to measure multiple cellular signaling events is essential to better understand the underlying complex biological processes that occur in living cells. Microarray-based technologies are now commonly used to study changes in transcription. This information, however, is not sufficient to understand the regulatory mechanisms that lead to gene expression changes. Here we present an approach to monitor signaling events upstream of gene expression. We coupled different reporter gene assays to unique expressed oligonucleotide tags (EXTs) that serve as identifiers and quantitative reporters. Multiple EXT reporters can be isolated as a pool and analyzed by hybridization to microarrays. To test the feasibility of our approach, we integrated complementation assays based on a protease from tobacco etch virus (TEV protease) and transcription factor activity profiling. Thereby, we simultaneously monitored Neuregulin-dependent mouse ErbB receptor tyrosine kinase dimerization, effector recruitment and downstream signaling.