In 1974, the Office of Policy Planning (OPP) was established within the Executive Department with the purpose of centralizing and systematizing the planning of Seattle's physical and social development. This organization was formed from the Office of Executive Policy (OEP), to which was transferred policy functions from a number of offices and departments, including Grants Management from the Office of Management and Budget (OMB), the Planning and Programming and Economic Development Programs from DCD, and all Comprehensive Policy Plan development efforts heretofore undertaken by individual City departments. OPP was designed with two principal divisions, Policy Management and Policy Development. The Law and Justice Planning division was added in 1975, and tasked with crime analysis and preventative planning. In 1975 the OEP's Intergovernmental Affairs Office was also incorporated into the OPP's Intergovernmental Relations Division.

In 1979, the OPP was converted into the Office of Policy and Evaluation (OPE), once again under the purview of the Executive Department. The new office's mandate was to oversee City planning, evaluation, and policy development activities. The main structural alterations were the removal of the Law and Justice Planning and Intergovernmental Affairs divisions and their subsequent elevation to Office-level positions within the same department. In addition, significant responsibilities and staff assets related to planning were transferred to DCD, including economic data analysis, housing, and citizen participation. The OPE was organized into three divisions: Policy Coordination and Management, Growth Management (changed to Special Policy Development Projects in 1980), and Urban Development and Issues (changed to Policy Analysis and Evaluation in 1980).

In 1982, the Land Use and Transportation Project (LUTP) was formed from those assets of the Office of Policy and Evaluation relating to planning and policy development for land use, transit and transportation, housing, and related economic development. Among the LUTP's duties was the generation of the Comprehensive Land Use Policies Plan, a comprehensive set of policy guidelines begun in 1978 and finally completed in 1986.

In 1986 the LUTP was consolidated into a new organization, the Office for Long-Range Planning (OLP). This new entity would be part of a general Planning Program within the Executive Department, along with the newly-formed Office of Strategic Human Services Planning (OSHSP), which would be responsible for human services needs assessment and related policy planning. In addition to LUTP's existing functions, the OLP was tasked with coordinating City policy for physical development, the environment and transportation; establishing a centralized planning database, and conducting long-range planning on issues deemed high-priority by the Mayor and the City Council. By 1989, the OLP was also assigned the job of administering effective City participation in regional planning initiatives, on topics like hazardous waste disposal and public transit.

In 1992 the Office of Long-Range Planning and Office of Strategic Human Services Planning were combined to create the new Planning Department, marking the first point since 1969 that planning and policy development for the City fell outside the direct control of the Executive Department. In addition to cultivating policy on land use, transportation, housing, the environment, human services, and urban design, the Planning Department's stated mission included the pursuit of local/regional planning collaboration as well as the evaluation of city policies for compliance with Washington's Growth Management Act and Seattle's Comprehensive Plan Framework Policies. The department was segmented into four divisions: Comprehensive Planning, Urban Research, Strategic and Special Projects, and Administrative. In 1995 the Planning Department and Office of Management and Budget were brought together to create the Office of Management and Planning.