This paper studies optimal informational control in contracts under the threat of collusion and its implications for organizational form. I consider a principal-supervisor-agent model: The agent is privately informed about his costs to realize a project for the principal. The supervisor observes a signal that is informative of the agent's costs. The supervisor and the agent may collude. The principal sets a contract and designs the supervisor's signal without being able to observe it. I analyze

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... the principal's trade-off between information elicitation and collusion prevention: A well-informed supervisor may provide good advice but can also organize collusion effectively. I study optimal signals and show that the principal wants to withhold information from the supervisor. Balancing upside potential and downside risk, the principal creates signal realizations of equal value that optimally incentivize the supervisor to participate in the contract. Given the optimal signal, the optimal contract can be implemented through delegation whereby the principal authorizes the supervisor to contract with the agent. I discuss implications for public procurement if corruption is an issue.