The precise control of living systems necessitates attention to many different parameters and often the exact values of these parameters are difficult to measure, control, and finely tune. One such parameter is plasmid copy number, in this work we demonstrate precise control of plasmid copy number in ColE1 origin plasmids. This control of plasmid copy number is accomplished in two ways, with an inducible system and a massively parallelized assay used for the generation of hundreds of copy number variants from a single plasmid backbone. This system is used to interrogate the physiological effects of plasmid copy number control on host cells as well as to control gene expression, optimize biosynthesis pathways, and modulate the behavior of a simple genetic circuit. Further, complex behaviors in cells are often difficult to engineer and present even further difficulties due to limited robustness and reliability. We demonstrate that oscillations in a simple network of three genes that mutually repress one another can be facilitated by the titration of transcription factors, which is facilitated by our tunable plasmid copy number system. Together, this work furthers the tools available to us for the precise control of living systems.