Biennial Appropriations Act - Amends the Congressional Budget Act of 1974 to require biennial (instead of annual) appropriations Acts, with the exception of annual defense appropriation bills.

Defines the budget biennium as the two consecutive fiscal years beginning on October 1.

Requires the committees of the House and Senate with legislative jurisdiction over an agency, in each year that the agency's activities are not required to be funded, to hold a joint oversight hearing on the impact of biennial budgeting on the agency with the corresponding subcommittee of the respective Committee on Appropriations with jurisdiction over the agency.

Requires the Director of the Office of Management and Budget (OMB) to: (1) determine the impact and feasibility of changing the definition of a fiscal year and the budget process based on that definition to a two-year fiscal period with a biennial budget process based on such period, and (2) report the findings to the House and Senate Budget Committees.