Transit planning has traditionally been approached from the point of view of a single, public operator that dominates transit service provision. Evolving transit market arrangements that have seen a larger potential role for the private sector in providing transit services in a competitive environment are bound to necessitate a transformation in the traditional transit planning approaches.The objective of this research is to revisit some of the transit planning tasks in view of such evolving transit market and regulatory arrangements. The paper investigates the implications of an evolving market arrangement, namely competitive contracting, on mass transit service design. Competitive tendering elements that relate to determining the size of the contract to be tendered as well as allocation of routes among bid packages (also known as Service Design) are addressed. The Modelling framework used in this research includes Optimal Frequency Determination of the bus routes, Transit assignment and Genetic Algorithm-based Optimal Bid Packaging components. The proposed methodology has been applied to a case study of the City of Mississauga, Ontario.