The Cowles Commission Archive at Yale provides a copy of Income, Employment, and the Price Level: Notes on Lectures Given at the University of Chicago Autumn 1948 and 1949 by Jacob Marschak. Notes edited by David Fand and Harry Markowitz, 1951. Problems, course examination (Fall 1949) and reading list are included.
See the biographical memoir for Jacob Marschak (1898-1977) written by Kenneth Arrow to appreciate the enormous debt modern economics owes to Marschak.
From the Course Announcements this would have been Economics 335, The Theory of Income and Employment offered in Autumn and Spring quarters. The notes explicitly refer to only the Autumn Quarters of 1948 and 1949. Oswald H. Brownlee was listed in the Announcements for the course for the Spring Quarter in 1949.
In the Evsey D. Domar Papers at Duke University’s Rubenstein Library, Box 16 c.1, folder “Final Exams: Johns Hopkins, Stanford, U. of Michigan”, there is a one page mimeographed page of final exam questions for “Economics 335, June 17, 1948” which is the time Domar had an joint appointment Cowles Commission/Department of Economics at the University of Chicago and corresponds to the precise end of the Spring quarter. Thus I consider it highly likely to most probable that Domar taught the Spring term, 1948 of Economics 335.
Image Source: Carl F. Christ. History of the Cowles Commission, 1932-1952.