Numerical simulations were performed to study the flow and mixing characteristics of two-dimensional laminar confined impinging streams. By solving the time-dependent conservation equations for mass, momentum and energy, Reynolds numbers beyond which the flow becomes oscillatory and even random were determined for different geometric configurations. Simulations were also performed for cases with jet Reynolds numbers in the stable regime to study the mixing characteristics of the system. It is found that both the inlet jet Reynolds number and the geometry of the system have strong effects on mixing in impinging streams.