Oscillator Based Ising Machines (OIMs) implemented on integrated CMOS circuits are a promising emerging technology. OIMs can solve combinatorial optimization problems in a fraction of the time while consuming several orders of magnitude less energy than conventional computing architectures. Their operating principle is based on the individually configurable coupling of many oscillators. The interaction inside the OIMs, which is key for the computation, has not been investigated extensively. This paper discusses the coupling of oscillators and draws attention to important design trade-offs. The unique challenges of transistor-based couplers are extensively discussed and a coupler circuit is proposed.